verb (used with or without object) Vulgar Slang.
to have sexual intercourse (with).
Origin of boink
First recorded in 1980–85; imitative of bouncing or banging
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
"have sex with; the sex act," slang by c.2000, perhaps an alteration of bonk in its popular sexual sense. Related: Boinked; boinking.
Online Etymology Dictionary, © 2010 Douglas Harper