n. An incompetent, foolish, or stupid person.n. A careless mistake; a slip.verb-intransitive. To make a silly mistake; blunder: goofed up by turning right instead of left. verb-intransitive. To waste or kill time: goofed around at the mall. verb-intransitive. To tease or make fun of someone: goofed on her younger brother. v. To spoil, as through clumsiness; bungle. Usually used with up: goof up a job.