You might use her name as an adjective: You might say somebody is Blairbrownish. It's hard to think of anybody else being Blairbrownish, but if they were, they would: talk a lot, and fast; have perfect diction; have pasteurized skin; combine pragmatic precision with stylistic flakiness (no la-de-da stuff here, pal); care emphatically about what they were doing while communicating the airiness of a space cadet, first class.

Have you ever noticed anybody being Blairbrownish around you? Probably not. In order to have spotted it, you would have had to have seen one of three movies:

* "One Trick Pony," which you didn't see, unless you either work for Warner Bros. or are a friend of Paul Simon's.

* "Altered States," which you might have seen, but in which the Blairbrownish qualities of the heroine were somewhat overpowered by the Kenrussellish light show.

* "Continental Divide," which you may not have seen yet because it just recently opened -- but in which the Blairbrownishness is wrestled down in the picture by the specified Hepburnishness of the tough Boston beauty she plays.

Blair Brown puts down her copy of the New Republic ("I love it," she says. "It's my favorite.") and frowns. "They're always comparing me to Katharine Hepburn," she says. "Always." That comparison hasn't caused many other actresses to complain, but nevertheless: "It's not that I don't think she's a great lady and a great actress," she says, "It's just that I'm always being compared to her and being told to play her parts." Blair Brown once played Tracy Lord in "The Philadelphia Story" at the Long Wharf Theater in Connecticut. "It was like playing Stanley Kowalski," she said. "Bossy, blind and arrogant." It was only one of her encounters with the Hepburn trail. "Once when I was reading for a part in a play she was in, she came up to me and looked me right in the face and said, 'You know, you look enough like me to be my daughter.' Well, I liked that -- Katharine Hepburn tells you you look like her daughter -- but then Richard . . ."

(Actor Richard Jordan, with whom she lives, and who is responsible for this, the fourth month of her pregnancy.)

"Anyhow, but then Richard was reading with her for something else and she walked right up to him and looked him in the face and said, 'You know, you look enough like me to be my son.' The two of us! The kids! So after that we were going to call her up and say, 'Hello, Mom, it's us! The kids!' "

Blair Brown laughs, showing beautiful teeth -- white and the product of exquisite care -- sure to become, with her Blairbrownish red hair, her trademark when she becomes marketable. She's not there yet. Even though she's an extraordinarily good actress, nobody remembers her parts. She's only had three movies, some television (a "Marcus Welby, M.D.," in which "I had to cry all the time because my father on the show had leukemia -- and it wasn't hard when I saw they'd put a hair attachment on me that looked like a Sara Lee") and theater in New York.

And yet Blair Brown is a hot commodity in Hollywood, one of the school of new young incidental stars who happen to be good actresses. She grew up in Washington where her father, Milton Brown, worked for the CIA. Their family of three lived in Arlington, Alexandria, Georgetown and McLean. "I remember getting taken out to the agency headquarters at McLean and walked around all the time," she says, "up to a checkpoint." She went to Madeira and then was shuttled off to Pine Manor Junior College near Boston. "It was filled with all these unbelievably rich southern girls, and outcasts like me. I was separated from boys, I shouldn't have been. I hated it, hated it," and she hated it so much that she was severely depressed and left.

She went up to the National Theater School of Canada during the '60s, after having had classic anti-war conflicts with her agency dad. "He kept on telling me I was wrong, and kept on saying he couldn't tell me why," she says. "That'll stop an argument fast." She lived with a guy "who was going to be the Jean Luc Godard of Canada, and Trudeau had just come in, and we all thought we were in paradise. But Canada got to be a little too much. I thought if I heard one more Gordon Lightfoot song I would kill somebody. They had a lot of talented people in Canada and a lot of them came to America. Thank goodness Anne Murray stayed there."

Brown was invited to work at the Guthrie Theatre in Minneapolis, and then went to New York for a couple of Joe Papp's plays before hitting it in his "Three Penny Opera." She went to California, got offered some work in television, and in a moment -- she was Blair Brown.

"But I'm not a star," she says, "and I couldn't help it, I wanted to be. I got typecast in the same part over and over -- urban and independent, strong-willed but not offensive. Actually, well, likably offensive." Which is exactly what she plays in "Continental Divide," the latest Lawrence Kasdan ("The Empire Strikes Back," "Raiders of the Lost Ark," "Body Heat") script to hit the country. Kasdan has a specific heroine in his movies, the "Kasdan woman," who fits neatly and somewhat infuriatingly into the Blairbrownish typecast -- of a woman who can handle herself, knows how to punch, punches, and in the second half of the picture usually submits to the male lead. In "Continental Divide," Blair Brown is Nell Porter of Boston, a dynamic enigma who cares for endangered eagles, watches them mate through binoculars, smashes hunters' shotguns against rocks, and falls for a Royko-like chain-smoking Chicago Sun Times columnist played by John Belushi. Brown wears tiny shorts, throws spears, saves lives -- and resolves it all in the end.

"I know, I know," she says, "it's the same thing all over. I want to play somebody who's hopelessly stupid, or has a limp, or a loser. I want to play heartbreaking people who are not going to make it, but they keep putting me in the same part. I want to play a singer! Like Rickie Lee Jones. I'm crazy about Rickie Lee Jones. I want to play Marjorie Kinnan Rawlings."

She smiles. "But it doesn't matter anyhow. I'm not really a star. There's an entire new school of cinematographers, who need to make their reputation by photographing things, not people -- who can get that look, and do it beautifully -- but it's not like the old days when the studio would say to the cinematographer, 'You make her look good or it's your a--.' People still don't recognize me.

"Just after we finished "Altered States," I went into this store, this kind of hip candle store, and I was on line. And I heard this guy behind the counter say that he had just seen this terrific picture last night, "Altered States," and that the two leads in it William Hurt and Brown were two actors he had never seen before and he told the woman he was selling to that they were great and she had to see it, and I was next on line, and I was sure this was my big moment and so I stepped up to the counter and looked at him and smiled and he looked at me, and he said,

" 'Oh yes, what would you like?' "

Blair Brown laughs and looks out from under her red fringe bangs and crosses her black paisley-knickered knees. "I've got to find better parts, and do better work, so they'll remember." She puts her hand on her four-months-pregnant stomach and says she's going up to Boston to play in "Man and Superman." "And if I get too big, there's a part for a pregnant woman in the play, and I'll just do that. That's all there is to it." She smiles most Blairbrownishly and begins to eat lunch for two.