a 'bonk-on' is another term used to describe an erect penis due to arousal
"my God Dave, did you see that girl?! she's fine! I've got a bit of a bonk-on now"
by TomTom20 June 23, 2008
Can you define these popular missing words?
"Bro, you have a bonk on"
by abbyl January 06, 2012