Yohji Yamamoto's description of a beautiful woman is hardly what you would expect from a leading designer. He begins: "Her age is about 40 to 50, her hair is gray or white and she is smoking a cigar. She's wearing a very simple T-shirt. She is standing at the water's edge at the sea; the wind is blowing. Always she's looking for the wind."

When pushed to say more about her clothes, he says, "I don't think about her clothes."

Yamamoto, 39, is at the forefront of the new wave of Japanese designers who stirred considerable controversy at the Paris collections in April. His clothes, dubbed by some as clothes for bag ladies, are usually oversized and often in dark fabrics; for the past year they have had an increasing influence on American and European designers.

"I know some say my clothes are black and dark and broken-down in shape," the designer said quietly in New York recently. But his departure from traditional, western clothes is intentional, he added. "It is important to live an independent way." Yamamoto rejects the old rules of clothes that limit them to certain times and occasions, and dismisses the idea that women should wear clothes a specified way.

"There is a freedom inside Yohji that expresses itself in his designs. He wants to break with what exists," said his business partner and former schoolmate, Goichi Hayashi. "If Yohji designed a glass, it would not look conventional. It would have a freedom and a flow. Above all, it would not follow tradition."

Yamamoto breaks with tradition in his personal life, too. "When my mother dies there will be a final ceremony with family and neighbors," he said. But he added that he would break with this centuries-old tradition when he dies.

His clothes change the rules on what is feminine and pretty and sexy. Yamamoto insists that when his oversized clothes brush against the body, the elbow, or the leg, they are sexy in a new way. "You begin to see the body in the drape of the clothes. To me that is very sexy," said Yamamoto.

He has no use for what he calls "the Playboy concept of beauty." He says, "If every woman was as pretty as in a magazine, that would be dull. I feel pretty or beauty in a girl or woman when I feel her loneliness or sadness.

"If a person is deeply educated and her mind is filled with many precious things, she should wear only dark clothes." Bright colors are disturbing, distracting, he says. "Color is the result of the shining light. It is different with each situation."

Color distracts like music when you are reading or studying, he says. "The music 'enfriends' you so you cannot create your own thing. You are given images from music. That is the same problem with color.

"The shape of my clothes depends on who wears them. The wearer is not responding to the shape of the clothes. The shape is coming from the man or woman wearing them," he insists.

"It is always a pleasant surprise to see someone in my clothes," he says. "There is no one way to wear my clothes, so each person shows me a new way to wear them."

Like many of the other Japanese designers, particularly Issey Miyake and his close friend Rei Kawakuba, the designer for Commes des Garc,ons, Yamamoto sees fabric as the starting point of all designs. "Fabric is 80 percent of the design," says Yamamoto, who draws on traditional Japanese fabric techniques mixed with modern concepts for his patterns and textures. Felt is patterned to look like tweed, cotton is wrinkled for texture. Tie-dyes mix with checks and tartans.

While most of his current fabric colors are subdued, there are bold patterned plaids, camouflage prints, combinations of black and gray and the characteristically Japanese black and blue. And there's an occasional flash of red and other colors.

His clothes are put together in layers of various lengths and shapes with tunics over pants and skirts or over other tunics, and dresses over dresses. Seasonally, there may be changes in proportion. A long tunic over pants; a shorter tunic over skirts. Pockets and bags, which may fall from straps or seams of the clothes, are always huge and functional and incorporate themselves into the design.

Yamamoto, who opened his boutique in Paris in 1980, graduated from Keioi University in 1966 with a law degree but without the proper connections to become a successful lawyer. So he enrolled in Bunka Fukosa, the fashion design school attended by Kenzo Takado and Kansai Yamamoto (not related to Yohji Yamamoto).

With the prize money from a school competition, Yamamoto took off for Paris and tried without success to sell his designs to fashion houses and department stores. When he returned to Japan he started working with his mother, Fumi, a tailor in Tokyo.

But his mother, who usually sits in the front row of his Paris showings and takes picture of her son's clothes and his friends in the audience, had ideas about clothes that are very different from her son's. They were too feminine, he said, and "not for the working woman." And so he struck out on his own.

Yamamoto likes to make the comparison of his own professional growth with that of Yves Saint Laurent. In 1977, when Yamamoto had his first showing in the Bell Commons in Tokyo, Saint Laurent was moving away from haute couture. "It was a time when fashion was becoming not just for rich women, but for all women."

Yamamoto's business has grown to a $25 million volume. Two years ago he showed his collection in Tokyo in a stadium where major tennis tournaments are held. "The kids yelled and carried on as if he were a rock star," recalls Terry Melville, Macy's fashion director, who was one of more than 9,000 people at the show. Now Yamamoto limits himself to two major shows for buyers and press in Paris.

When he shows his collection in Paris next October there won't be any drastic change in the clothes. Certainly nothing will ever be tight. "It doesn't look noble to me," he says. "Also, it is not polite to show off too much."