1. Have sexual intercourse with.
2. To hit, particularly hitting a person on the
head.
3. During the hayday of MUDs (Multi-User Dungeon games, text-only roleplay like adventure games played mostly over the net) a commonly
said or done action as a sign of mild disapproval or for no particular reason. Polite convention require(d/s) the bonked individual respond by saying oif. Some believe not doing so
will upset the bonk/oif balance in the universe, with great consequences. Not saying "oif" is somewhat akin to a ( without a ) or unmatched quotation
mark. The practice is still somewhat alive on IRC and (to an
even lesser degree) other means of net chat. It has, however, to a large degree been replaced by the fish
slap.