1337 hax means literally "Leet hacks" or "Powerful/Uber hacks"
Basically, a 1337 h4xor uses 1337 hax.
World of Warcraft Term (common).
If somebody is using speed hacks or any other hacks in WoW, people say..."Dude, 1337 hax"
"Zomg, 1337 hax brah"
"rofl, 1337haxxx"
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