Active
Active is a term used in evaluating whole board positions, mostly in the opening. Presumably it originates from the fact that Black has to overcome komi. It is not necessarily always better than the alternative, but it reflects an attitude which is regarded positive in (Korean) textbooks. Active play may refer to taking sente and using it to attack the opponent's positions or building a big moyo.
In general it is the opposite of passive, which is associated to slow play, taking gote excessively, to the point of following the opponent around.