To 'Bog-wash', noun.
To 'bog-wash' somebody is to force their head into a toilet bowl (almost without exception against their will) before flushing, thus soaking the victim.
Bog-washing was popularised in Britain in the late '70's as a result of kids TV show Grange Hill. Usually 'Doyley' would grab an unsuspecting first-former and subject him to a bog-washing for 'shits and giggles' before inevitably being caught in the act by either;
a) Hard Assed PE teacher Mr.Jenkins or
b) Tucker Jenkins (no relation) and his friend Alan, who would then administer some form of childhood punishment on the unfortunate Doyley.
Gripper Stebson continued the bog-washing tradition in the '80's although in the far more sinister pursuit of bullying Roland Browning and nicking his dinner money.
Luckily I managed to avoid getting bog-washed during my school days, I did however receive the occasional wedgie, peanutting and beano.