look up anything, like your first name:
1. Doing a John
Entering a public toilet and using the facilities improperly; often involves leaving faeces in the toilet bowl without initiating the flush mechanism.
"See that bloke over there, the one with a newspaper, he is doing a John."

"Dirty bastard"
by Graham Marsh Oct 22, 2004 add a video
2. Doing a John
Lusting after a young girl with the intention of postponing a sexual proposition for an undetermined number of years.

Often the perpetrator will announce the number of years he intends to wait in a grumbled tone.
So my little sister just started junior school. Yeah, she is doing really well, better than I was at that age. Hey John, I won't be in lesson because I've got to go and pick her up at three.

Four more years...
by Graham Marsh Oct 24, 2004 add a video
3. Doing a john
to unexplainably lose all your money in five hands of poker
'Damnit five hands and im all out!'
'shut yo jibba jabber and stop doing a john!'
*crys then begins to masterbate*
rss and gcal