adjective

1. making no vocal sound; not speaking; speechless; mute
2. seldom speaking; saying little; not talkative
3. free from, or not making, sound or noise; quiet; still; noiseless
4. 1. not spoken, uttered, or expressed silent longing
   2. included in the spelling of a word but with no part of the word's pronunciation corresponding directly to it: said of a letter or group of letters silent b in “debt” and gh in “thought”
5. withholding knowledge or omitting mention; uncommunicative
6. not active factories silent for months
7. designating or of films without a synchronized soundtrack
8. not having noticeable symptoms a silent heart attack

Etymology: L silens < prp. of silere, to be silent, still, prob. < IE base *sē(i)-, *sī-, to rest > seed, side, Goth (ana)silan, to cease (of the wind)

noun