piffle

nouns

trivial nonsense
balderdash, fiddle-faddle, piffle

verbs

speak (about unimportant matters) rapidly and incessantly
blab, blabber, chatter, clack, gabble, gibber, maunder, palaver, piffle, prate, prattle, tattle, tittle-tattle, twaddle
act in a trivial or ineffective way
piffle
is a type of (narrower)
behave in a certain manner; show a certain behavior; conduct or comport oneself
"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"
act, behave, do