a sandwich short of a picnic

one sandwich short of a picnic

A pejorative phrase meaning not very intelligent or of questionable mental capacity. It can appear in many different forms and variations (for example: one card short of a full deck, one brick shy of a full load, etc.). He says he's going to start a business selling bees as pets—I think he may be one sandwich short of a picnic. The new manager is nice enough, but he's one sandwich short of a picnic, if you ask me.
See also: of, one, picnic, sandwich, short

a sandwich (or two sandwiches) short of a picnic

(of a person) stupid or crazy. informal
See also: of, picnic, sandwich, short