look up any word, like potate:
 
1.
'Slag' (dog,devious,untrustworthy,grass) 'Boat' (face)
A slaggy boat. Somebody considered untrustworthy, reguarly pulling snakey moves on friends and just generally being a c*nt. Hangs about with gangster crowd pretending to be a drug dealer type but never sold a penny's worth.
That paul's a right slagboat - I've got no time for the geezer.

John, you cheeky fu*king slagboat wheres my puff?!?
by HACKMODE February 09, 2012
 
2.
Whilst a boy is going out with a girl, when with his mates, if one of them asks wheres 'slag boat' they mean where is your girlfriend.
A slang term used to identify your girlfriend.
Andy: " Wheres Slag boat?"
Dave: "She is at home"

Andy: "Your slag boat is getting on my nerves"
Dave: "Sorry mate, i will have a chat with her"
by bondy boy November 22, 2007