Bad Aji
Unpleasant possibilities remaining for one player in a position, after a local sequence has been played out. Any out of shortage of liberties, cutting points, an invasion, or a ladder where the captured stone remains on the board, can constitute bad aji
In most cases the problem could be fixed with a further play, but that would be too slow at the given stage of the game. Having bad aji is likely to be a disadvantage in complex fighting, since the opponent will try to exploit it.
The converse to the proverb play away from thickness is that one should try to lead the fighting into the vicinity of the opponent's bad aji. The other main way to use it is by means of a ko fight.