Same as "Wanker" .... one who "wanks" and one who "tosses" .....
ETA:
Wiki Wanker
I've given up trying to understand most of it, but the UK guys are a funny bunch.
As in "polishing oneself".....

Tosser = jerk off, noun rather than verb

The best place for slang and the like is
Urban Dictionary I work in IT and several systems have passwords from there... we used to have one system that was "monkeyface"... look it up

Would have loved him to do this on That's Life Esthers face would have been a picture

Doc Cox from "That's Life" ...
Originally Posted By lynk:
The best place for slang and the like is
Urban Dictionary I work in IT and several systems have passwords from there... we used to have one system that was "monkeyface"... look it up

makes a change from frodo12 I suppose....
To toss or wank, describes the act you Americans would recognise in Americanisms such as "jerk off", "spank the monkey" or my favourite "flog the log".
Therefore a tosser is someone who partakes in the previous activity.
Tosser or Wanker are intechangeable, and are generally used as a derisory term for a person for whom you have little regard. It is a fairly lightly used term now, and even an extreme case (a fu*king tosser) will generally not produce extreme offence, for which we have to use other words.
Here is a link to an old comedy series that shows schoolboys using the term in it's correct context.
http://www.youtube.com/watch?v=wRPXpA6BLUY
Ok,
I think he has the idea now

There is also: "choking the chicken!".
Stop it now.