thwap exclamation 1verb 1forms 3 exclamation1 •The sound of a heavy smack.THE COMPLETELY MAD DON MARTIN, a two-volume honker that includes every drawing Martin ever published in the magazine, answers the question with a definitive thwap: Martin's cartoons are still weird. — 2007 verb1 •To make, or cause to make, a heavy smacking sound.Reflectors in the road thwapped beneath the tires, setting a regular, almost reassuring pace. — 2004 formsthwapped · thwapping · thwaps