Means: The Addicting Abbreviation Game. The rules are:
one person (the it person) chooses a set of letters from three letters to five, and the rest of the group has to make things that it stands for. Whoever's it chooses the wittiest one. If the letters were 'sh' then a possible match for it might be 'she hates hats' or 'several hats hate'. No names allowed.
Person One: Let's play Taag!
Person Two: Ugh, let's not.