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
2 more definitions
A gentleman's secret part in a state of some arousal.
By Jove, she could be Helen of Troy! She could enjoy the expert favours of my inserting my bonkon into her bearded clam any day of the week, sirrah!
by The Squire July 24, 2003