A Star Trek fan (or Trekkie) who's primary or only interest is in the Original Star Trek series (The Orignal Series, or TOS). TOSsers almost always prefer to refer to themselves as simply Trekkies; TOSsers is a term applied to these old-timers by fans of the newer shows.

Literally, one who masturbates. Common usage typically refers to anyone of whom you have a low opinion.

English insult.
Implies that the person masturbates excessively. Also see Wanker.

Useless, pathetic, incapable of doing anything right

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.

another way to say wanker.

As far as I'm aware tosser has nothing to do with mastubation but comes from an old sailing term for a drunken idiot - 'he's a toss pot' - ie someone who drinks a lot is a tosser or toss pot.

Noun, British slang; slightly offensive term: dick head, jerk, idiot, bit slow and rough, a non-violent bully, loud and rude + not brightest bulb on the tree.

Verb, Toss off, British slang for male masturbation; not the same meaning as the noun "Tosser."