1. Someone so irredeemably idiotic that it is safe to assume that they derive pleasure from slashing cocks... possibly with a blade of some sort, we just don't know.
2. A general term for an annoying or stupid person.
3. A generic insult, can easily deployed as it rolls off the tongue like water off a Goretex duck.
(Commonly accredited to the legendary Bruce)
'What a cock slasher, he just spat on my patio'
'You cretinous cock slasher, since when have you had the glands to stand up to me'
'AAAAAAARRRRRGHHHHHH!!!! You COCK slasher, right on the tip!'