adj

• (mathematics, logic) Having the property of soundness.
  "With fresh material, taxonomic conclusions are leavened by recognition that the material examined reflects the site it occupied; a herbarium packet gives one only a small fraction of the data desirable for sound conclusions. Herbarium material does not, indeed, allow one to extrapolate safely: what you see is what you get[…]"
• (British, Ireland, slang) Good; acceptable; decent.
  "How are you? —I'm sound."
• (of sleep) Quiet and deep.
  "Sound asleep means sleeping peacefully, and often deeply."

intj

• (British, Ireland, slang) Yes; used to show agreement or understanding.
  "I found my jacket. — Sound."

noun

• (music) A distinctive style and sonority of a particular musician, orchestra etc.
  "He looks like he's got it, maybe. Listen to those kids!/There's no maybe about it. That's it, that's the sound."
• (phonetics) A segment as a part of spoken language, the smallest unit of spoken language, a speech sound.

verb

• (intransitive) To produce a sound.
  "When the horn sounds, take cover."
• (copulative) To convey an impression by one's sound.
  "He sounded good when we last spoke."
• (intransitive) To be conveyed in sound; to be spread or published; to convey intelligence by sound.
  "For from you ſounded out the worde of the Lord, not in Macedonia & in Achaia onely: but your faith alſo which is towarde God, ſpred abroade in all quarters, that we nede not to ſpeake any thing."
• (intransitive, obsolete) To resound.