Originally posted by Toeer - you're third example backed me up, but never mind.
erm, its slang here: there ain't no "correct" slang.
If you want to use the www as reference, try
http://www.peevish.co.uk/slang/s.htm
"Verb To put down, verbally. Meaning the same as 'slag off'"
or
http://www.thecraic.net/glossary.html
"...In the Midlands, if people don't slag you unmercifully, it's a sign they probably don't like you."
or
h ...[text shortened]... little room for correctness. By it's very nature it will be modified by the group that uses it.
I agree that slang can be very, erm, geographic!
I might start a thread to see if people from different parts of the world have different "slang" words, but I'm sure it's been done before.