It is a derivative of the derivative of noob. Always offensive, it is reserved for the most persistant and stupidest of the noobs. Often neeblets call experienced players noobs or nooblets, believing that because they won't give them free stuff they are stupid and nooby.
The biggest difference between a noob and a neeblet is that neeblets insult and threaten people they are begging from.
Neeblets usually go nowhere in the game and end up quitting "Cause everyones a f***ing n00blet"
N338137 (used by one neeblet calling someone else a neeblet)
Person 1: No you noob!
Neeblet: G1V3 m3 Phr33 St00fz0rz oR 1 VVi11 haX0r j00z0rz W17h M3 1337 5k1llsz0rz, j00 N00bl37!
Person 1: (walks away)
Neeblet walks two steps away to person 2, who saw the entire thing and repeats the process with different experienced players begging, threatening, then finally insulting and moving on.