WordNet sense 1 (a deaf person who is unable to speak):

deaf-mute, deaf-and-dumb person

WordNet sense 2 (deaden (a sound or noise), especially by wrapping):

damp, dampen, dull, muffle, tone down

WordNet sense 3 (lacking power of speech):

tongueless

WordNet sense 4 (not capable of or especially not involving speech or spoken lines):

nonspeaking, walk-on

WordNet sense 5 (expressed without speech; especially because words would be inappropriate or inadequate):

unspoken, wordless

WordNet sense 6 (unable to speak because of hereditary deafness):

dumb, silent

WordNet sense 7 (without or deprived of the use of speech or words):

unarticulate