Definition: act foolishly, as by talking nonsense
Definition: behave in a certain manner; show a certain behavior; conduct or comport oneself
Usage: You should act like an adult; Don't behave like a fool; What makes her do this way?; The dog acts ferocious, but he is really afraid of people
Definition: be about
Usage: The high school students like to loiter in the Central Square; Who is this man that is hanging around the department?
Similar words: be
Definition: have the quality of being; (copula, used with an adjective or a predicate noun)
Usage: John is rich; This is not a good answer