In the second episode of HBO’s “Girls,” three young women are eating frozen yogurt on a park bench: Jessa, the slutty one, Shoshanna, the prudish one, and Hannah, our protagonist. After Hannah expresses frustration with her pseudo-boyfriend, Shoshanna whips out a copy of a fictional advice book: Listen, Ladies: A Tough-Love Approach to the Tough Game of Love.

Hannah: Wait, but here’s my question: Who are the ladies? Shoshanna: Obvi. We’re the ladies. Jessa: I’m not the ladies. Shoshanna: Yeah, you’re the ladies.

The exchange is a perfect who’s-on-first for the urban twentysomething: the word “lady” has become core vocabulary of feminism in the age of irony. With its slippery meaning—associations range from grandma’s lavender-scented powder to the raunchiest of rap lyrics—it encapsulates the fundamental mutability of modern feminism. To quote Britney Spears’s 2002 power ballad, many of the female gender today think of themselves as “Not a Girl, Not Yet a Woman.” “Lady” has come to occupy the middle ground.

This is new territory for an old and loaded term. “Lady” once implied a proper woman who is not to be disrespected, crosses her legs at the ankle, and never talks out of turn. She doesn’t work; she lunches. Later, of course, it was adopted as a catcall (and cattle call) in the style of the late-’80s Beastie Boys. “I threw the lasso around the tallest one and dragged her to the crib,” they rapped in “Hey Ladies.” Then there were the gender-specific drink specials at your local dive.

But even as the term got raunchier, the “Downton”definition persisted. (See Vanity Fair’s February issue, which features lush watercolor paintings of “Downton Abbey”’s Michelle Dockery, creatively titled “Portrait of a Lady.”) Rappers still distinguish between ladies in the street and freaks in the bed. (Thank you, Ludacris.) A new, self-published advice book called Dare to Be a Lady “explores what it means to be a lady in a world where high moral standards are not often upheld and women often behave like men.” In response to a get-out-the-vote video by Lena Dunham and other hip, young liberals, the fusty conservative group Concerned Women for America called its counter-campaign “Lady Smarts.”

“Lady” splits the difference between the infantilizing “girl” and the stuffy, Census-bureau cold “woman.”

This morally loaded and intellectually unserious interpretation meant feminists in the 1960s and ’70s objected to the term, especially in professional contexts. “[T]he more demeaning the job, the more the person holding it (if female, of course) is likely to be described as a lady,” wrote the feminist linguist Robin Lakoff in a 1973 academic paper. “Thus, cleaning lady is at least as common as cleaning woman, saleslady as saleswoman. But one says, normally, woman doctor. To say lady doctor is to be very condescending.” Lakoff pointed out that no such dichotomy existed for men: “Garbage man or salesman is the only possibility, never garbage gentleman.” Likewise, feminists argued, “woman” should be the neutral default.