Alexandra (Estelle Parsons) knows her way around a Molotov cocktail.

“Being old is such a different part of life,” actress Estelle Parsons says. “Your outlook changes. Like, I was putting in for a grant for this female ‘King Lear’ project I’m working on, and one of the questions was, ‘What are your plans for the future?’ I put, ‘I’m 85. I’m not really having a lot of plans.’

“I didn’t get the grant,” she says. “I guess that was the wrong answer.”

Aging is the central theme of Arena Stage’s “The Velocity of Autumn,” in which Parsons plays Alexandra, a 79-year-old who lives alone in a Brooklyn brownstone. Instead of filling her time with needlepoint and “Wheel of Fortune” played REALLY LOUDLY on the television, she’s amassed enough Molotov cocktails to take down her entire block in an effort to prevent her two daughters from putting her in a nursing home.

Her son (played by Stephen Spinella), the other half of the two-person cast, climbs through her window to prevent this particular raging against the dying of the light. Alexandra tells him about her life, so it’s like storytime with Grandma, except there are snipers gathering on the surrounding rooftops.

“[Director] Molly [Smith] sent me the play and I really wanted to do it because I loved the character,” Parsons says. “And I liked what the play talked about, which is old age and dying, and how you want to die, and are you going to fight for what you want, even if it’s going to be a losing battle?”

That sounds depressing, but “Velocity” has plenty of humorous moments that play to Parsons’ comedic strengths. (To younger audiences, she’s probably best known as Roseanne’s mother on the TV series “Roseanne.”) Film buffs also know she won an Academy Award as a supporting actress in 1967 for her role as gang member Blanche in “Bonnie and Clyde,” directed by the legendary Arthur Penn.

“After I won the Academy Award, I called up Arthur to thank him for hiring me,” she says. “I was crying and I said, ‘What shall I do now?’ He said, ‘You go on doing what you do.’ ”

And that’s what she’s done ever since. She may not be “having a lot of plans,” but she’s excited to see what the future holds. “Eva Marie Saint told me the fun part of life is wondering what you’re going to get,” she says. “Because once you’ve got things, you’ve got them. The fun part of life is looking forward.”

Arena Stage, 1101 Sixth St. SW; through Oct. 20, $85-$105; 202-488-3300. (Waterfront)