be anyone's

be anyone's

To be promiscuous (and thus easily wooed by anyone). I'm not surprised he left the bar with that girl—he's anyone's these days.
Farlex Dictionary of Idioms.

be anyone's

(of a person) be open to sexual advances from anyone. informal
Farlex Partner Idioms Dictionary
See also:
  • on one's
  • on someone's
  • pillow-biter
  • (Have you) been OK?
  • (something) blows
  • (Can I) give you a lift?
  • out of one's
  • (I've) got to go
  • #dead
  • save someone's skin
References in classic literature
"It is all very well for Rostov, whose father sends him ten thousand rubles at a time, to talk about not wishing to cringe to anybody and not be anyone's lackey, but I who have nothing but my brains have to make a career and must not miss opportunities, but must avail myself of them!" he reflected.
War and Peace
Other children seemed to belong to their fathers and mothers, but she had never seemed to really be anyone's little girl.
Secret Garden
I "straw my way" with herbs, until any-a-day in port, to join crew--stand tight to mast, be brunt of wave and windlash, and not be anyone's burden except, oh, the crew, the crew, the which a-one I'll my love to, my goods and ghastly goofs.
Laughed-At Heart
As it is, I'm not sure you're suited to be anyone's wife, or a mother for that matter.
Just Joan: We're arguing over a big wedding
So many wrinkly rockers seem to like pottering around the garden, they could be anyone's granddad.
Every whiff you take. .
Everyone thinks I must be desperate to get off the shelf, but although I love this man and I am sure he loves me, I don't think I want to be anyone's wife.
Just Joan: NEXT WEEK'S PROBLEM ..