An abbreviation for "Adventure Quest Worlds", a free-to-play MMO seeming to be aimed at a somewhat of a 'younger audience', but there are more teenagers than young children that play.
*chatting on Facebook*
Jeffrey: Hey Bob! How's it going?
Bob: Playing AQW, trying to lvl my healer class...
Jeffrey: I stopped playing that over a year ago because half the population is younger than me. Play some REAL games, man!