In need of cash — we’ll get to why in a minute — Elle Reid, a poet and sometime professor in her 70s, decides to sell some precious old books. She figures that even though they’re a bit worse for wear, her first editions of Betty Friedan and Simone de Beauvoir should fetch a few hundred dollars at the local feminist bookstore-cafe. Her outrage when she’s grudgingly offered a lot less than that compounds her dismay at her teenage granddaughter’s cluelessness about the authors of "The Feminine Mystique" and "The Second Sex." What’s wrong with the world these days?

That’s a long conversation, but as of this writing one thing that is absolutely right with the world is the existence of "Grandma," Paul Weitz’s wry and insightful movie about an eventful day in the life of Elle and her granddaughter. There is much to praise about this sweet, smart comedy of intergenerational conflict and solidarity: the way the script captures the speech patterns of the young, the old and the middle-aged; the way the story feels at once frantic and relaxed, as the two main characters race against the clock and meander through Los Angeles in Elle’s wheezy vintage car; the brief, memorable appearances from supporting performers like Judy Greer, Sam Elliott and Elizabeth Pena (in one of her last roles). But honestly, the wonder that is "Grandma" can be summed up in two words: Lily Tomlin.

I’ll spare you a lecture on the historical significance and cultural import of Tomlin, and her particular relevance to the popular culture of 2015. On second thought, I won’t. Too much gets taken for granted these days. And while Tomlin has been a consistent presence on television, in movies, in recordings and onstage for roughly the past half-century — from "Laugh-In" to "The Search for Signs of Intelligent Life in the Universe" to "All of Me" to "The Magic School Bus" and beyond — she is currently having a bit of a renaissance, thanks to this movie and to "Grace and Frankie," the Netflix sitcom that splendidly pairs her with Jane Fonda. (I will save my lecture on the zeitgeist-transcending awesomeness of Fonda for another time.)

"GRANDMA" Rated: R Opens Friday at Kahala 8

It’s fitting that this renewal of attention arrives amid a flowering of feminist comedy, and worth acknowledging Tomlin’s status as a foremother — a big sister, a wild aunt, however you want to put it — of the frank, fearless, funny women who have recently rescued American humor from its bro’ed-out doldrums. Tina Fey, the Amys (Poehler and Schumer), the ladies of "Broad City" and the shape-shifters of the current "Saturday Night Live" cast did not come out of nowhere. To revisit Tomlin’s old LPs or videos of her one-woman shows is no more a matter of nostalgia than Elle’s embrace of de Beauvoir and Friedan. It’s a matter of memory, of understanding the continuities and ruptures of history. And that’s the truth.

For Elle, this truth is personal as well as political, and anything but simple. "Grandma" is, among other things, a portrait of grief. For more than 30 years, Elle shared her life with Vi, whose relatively recent death casts a long shadow over Elle’s daily routines. In the first few scenes, we see Elle brutally dumping her younger lover, Olivia (Greer), and then weeping alone in the shower once Olivia has left. Bereavement, it seems, has set Elle firmly in her solitary, sarcastic ways. She doesn’t talk much to Judy (Marcia Gay Harden), the daughter she and Vi raised together, and is therefore somewhat startled when Judy’s daughter, Sage (Julia Garner), shows up at her door in need of help.

Sage is pregnant. She has an appointment for an abortion but not enough money to pay for it, and Elle, in a quixotic gesture of rebellion that is also a convenient plot device, has recently shredded her credit cards. Hence the trip to the bookstore-cafe (where Olivia happens to be working), and hence the zigzagging mini-road trip, during which they encounter Sage’s jerky ex-boyfriend (Nat Wolff), an old flame of Elle’s, and Judy, who makes both her mother and her daughter nervous, though for different reasons.

"Mom says you’re a philanthropist," Sage says to her grandmother. The word she’s looking for is misanthrope, but of course there is a core of tenderness and generosity underneath Elle’s caustic surface. That might be the wrong way to put it. What Weitz and Tomlin understand about the character, and about many other feminists of her generation, is that her grouchiness and her compassion issue from the same source. She is impatient with the world and suspicious of the motives of a lot of people in it, but that is partly a result of her idealism, her uncompromising commitment to behaving like a free human being.