A sexual history which in hindsight was astronomically stupid.
Can be used not only to refer to the event of sex, but also to the individual one now deeply regrets touching and being touched by in one's intimate places. Can refer either to a one night stand (most common), or a series of sexual encounters (i.e. fuck buddy).
The individual recounting stories of their sextake may surprise listeners with how idiotic their sextake was: "a shady as fuck porn baron prone to incredible douchebaggery who could barely keep it up and who I really only clung to as a temporary salve for loneliness."
Like a mistake you made in sex!
"That douche was my... sextake."
A: "You know what that was?"
B: "I don't know. It was a sexual encounter with a complete tool. What would you call it?"
A: "A sextake."
The only thing more regrettable than a sextake? An STD.