Derived from roflcopter from the Blizzard forums of Warcraft III, nubcopter is a derogatory term used to make fun of a nub who tries to rape with the uberly powerful roflcopters and failz. After such an embarrassing fail, someone will take a screenshot and post it on the forums, thus causing everyone to call him a nubcopter.
Lildude: MWAHAHAHAHAHAHAHA! I AM GOING TO RAPE JOO WITH MY MASSIVE ARMY OF DESTRUCTIVE ROFLCOPTERS...FEEL MY WRATH!!
*massive army of roflcopters get destroyed within 4 seconds*
Zaryl: LOL! WAT A NUBCOPTER! I JUST HAD A ROFLGASM...AHAHAHAHA WAT FAILZ!