ok, here's the true
explanation:
while the word
wanker is a more general and term for expressing
disdain for somebody, the word tosser describes a person with a tendency to show off or brag in an excessive and embarrassing way.
or someone whose explanation of a word consists solely of another synonym.
"well at first i thought this guy delivers, but
in the end he was just another tosser."
A asks: hey, what does tosser mean?
B answers: duh, it means:
wanker.
A thinks: what a tosser.
B thinks: damn,
i'm smart...
;-)