Wiktionary
doink
n. (context slang English) A fool; a jerk; a worthless person. vb. (context US slang humorous transitive English) To have sexual intercourse (with someone)
Usage examples of "doink".
Owen looked extremely susceptible to tickling, which he was, and Hester's gesture was of the friendliest of intentions-especially for Hester-but the combination of putting his hand on live hair, in the dark, coupled with being tickled by a girl who, Owen thought, was merely tickling him en route to grabbing his doink, was too much for him.
I will confess that in the showers in the Gravesend Academy gym-after practicing the shot-I had noticed that Owen's doink was especially large.
I confess: I don't know-I have no doink theory as adamant or hopeful as Simon's.