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1. Taking more than usual time to learn or understand; lacking intellectual acuity
   "dumb officials make some really dumb decisions"
   - dense, dim, dull, obtuse, slow
    
2. Temporarily incapable of speaking
   "struck dumb"
   - speechless
    
3. Lacking the power of human speech
   "dumb animals"
    
4. Unable to speak because of hereditary deafness
   - mute, silent
    
5. Devoid of good sense or judgment
   - foolish, stupid, daft

1. Make simpler and less intellectually challenging (in a negative sense)
   - dumb down

Derived forms: dumbest, dumber, dumbing, dumbs, dumbed

See also: absurd, asinine, cockamamie [N. Amer], cockamamy [N. Amer], cockeyed, derisory, dumbly, dumbness, fatuous, fond, goofy, harebrained, idiotic, ill-advised, ill-conceived, impolitic, imprudent, inadvisable, inane, inarticulate, insane, laughable, ludicrous, mad, mindless, misguided, nonsensical, preposterous, rattlebrained, rattlepated, ridiculous, sappy, scatterbrained, scatty [Brit], silly, stupid, unadvisable, unadvised, unarticulate, unwise, vacuous, wacky, whacky, zany

Encyclopedia: Dumb