thick as a plank

Adjective

Meaning

thick as a plank (not comparable)

(simile, informal) Very stupid.
Synonyms: thick as a brick, thick as two short planks; see also Thesaurus:stupid

Source: en.wiktionary.org

Synonyms

mentally retarded

Antonyms

capable versant well-educated razor sharp

Examples

I'm as thick as a plank. Diana, Princess of Wales

Close letter words and terms

thick angle thick around the middle thick as a brick thick as a whale omelette thick as champ thick as flies