dumb

Adjective
  1. Slow to learn or understand;
    Lacking intellectual acuity (synset 300442596)
    "so dense he never understands anything I say to him"; "never met anyone quite so dim"; "although dull at classical learning, at mathematics he was uncommonly quick"; "dumb officials make some really dumb decisions"; "he was either normally stupid or being deliberately obtuse"; "worked with the slow students"
  2. Temporarily incapable of speaking (synset 300153897)
    "struck dumb"; "speechless with shock"
  3. Lacking the power of human speech (synset 300153272)
    "dumb animals"
  4. Unable to speak because of hereditary deafness (synset 300153123)

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