Lackbrained

Part of speech: adjective

Definitions

1. Foolish or lacking intelligence and good judgment
2. Exhibiting poor judgment or an absence of clear thinking
3. Displaying a deficiency in mental sharpness and practical sense

Etymology: "Lack" in this word is the old noun meaning a shortage or defect, not the verb "to be without." English took the noun from Middle Low German or Middle Dutch, where a related word meant a fault or flaw, and it was used in that sense long before the verb became common. The second element is "brain," turned into an adjective with "-ed," so the compound literally means "having a defective brain." It follows the same pattern as "hare-brained" and "feather-brained," where a body part names the faculty being faulted. Exact dates of first appearance for this particular compound are uncertain, so it is best understood as a transparent formation from its two parts.

Synonyms: foolish, silly, stupid, mindless, obtuse

Antonyms: intelligent, smart, wise, clever, bright