Means: Someone who cheats
Usage: "Miss, Perry's a glicther; he's copied off the internet."
This weird-looking, odd-sounding word started out as a deliberate rewriting - what sociolinguists call a "creative re-spelling" - of "glitcher". Still baffled? Well, many video games have inbuilt glitches - errors in the programme - that can be discovered and then exploited by unscrupulous players (glicthers) to win unfairly or outsmart opponents, so: "I'm organising a glicther clan. You wanna join?"
The venerable tradition of messing with spellings began with US street culture's use of "phat" and "tuff", substituting its own plural "z" (as in "doodz", "hackerz and crackerz"), then the Yoof began to parody online misspellings (like "pwned" for owned) and the SMS predictive text errors by which "cool" comes out as "book". Mercifully, most kids are savvy code-switchers and (we hope) don't carry the practice over into school writing assignments. In the case of glicther, what was formerly a written gimmick is now said out loud, to the confusion of any passing adult and probably a few fellow pupils, too.