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% replaces any number of letters (la% - lake, lamp)_ replaces one letter (ca_ - car, cat)

Crossword clues for Really, really dumb:

BONEHEADED: Really, really dumb
DOLT: Really dumb person
DOOFI: Really dumb people, facetiously
MORONIC: Really dumb
INANE: Really dumb
DODO: Extinct bird that wasn't really "dumb"
THICKO: Really dumb person, in British slang
IDIOTIC: Really dumb