dumb 
(dŭm)
(dŭm)adj. dumb·er, dumb·est
1.
a. Lacking the power of speech. Used of animals and inanimate objects.
b. Offensive Incapable of using speech; mute. Used of humans. See Usage Note at mute.
2. Temporarily speechless, as with shock or fear: I was dumb with disbelief.
3. Unwilling to speak; taciturn.
4. Not expressed or articulated in sounds or words: dumb resentment.
5. Nautical Not self-propelling.
6. Conspicuously unintelligent; stupid: dumb officials; a dumb decision.
7. Unintentional; haphazard: dumb luck.
tr.v. dumbed, dumb·ing, dumbs
Phrasal Verb: To make silent or dumb.
dumb down (or up)
Slang To rewrite for a less educated or less sophisticated audience.
[Middle English, from Old English.]
dumbly adv.
dumbness n.