From WordNet (r) 3.0 (2006):
silent
adj 1: marked by absence of sound; "a silent house"; "soundless
footsteps on the grass"; "the night was still" [syn:
silent, soundless, still]
2: failing to speak or communicate etc when expected to; "the
witness remained silent" [syn: mum, silent]
3: implied by or inferred from actions or statements; "gave
silent consent"; "a tacit agreement"; "the understood
provisos of a custody agreement" [syn: silent, tacit,
understood]
4: not made to sound; "the silent `h' at the beginning of
`honor'"; "in French certain letters are often unsounded"
[syn: silent, unsounded]
5: having a frequency below or above the range of human
audibility; "a silent dog whistle"
6: unable to speak because of hereditary deafness [syn: dumb,
mute, silent]