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Phrase(s): a few bricks short of a load [and] a few cards shy of a full deck; a few cards short of a deck; not playing with a full deck; two bricks shy of a load
Fig. lacking in intellectual ability. (Many other variants.) • Tom: Joe thinks he can build a car out of old milk jugs. Mary: I think Joe’s a few bricks short of a load. • Ever since she fell and hit her head, Jane’s been a few bricks short of a load, if you know what I’m saying. • Bob’s nice, but he’s not playing with a full deck. • You twit! You’re two bricks shy of a load.
McGrawhill's American Idioms And Phrasal Verbs