Synonyms of the word

unsounded

• adj. unfathomed.

deep

• adj. (heading, of a physical distance) Extending far away from a point of reference, especially downwards.
• adj. (heading, intellectual, social) Complex, involved.
• adj. (sound, voice) Low in pitch.
• adj. (of a color) Dark and highly saturated.
• adj. (sleep) Sound, heavy (describing a state of sleep from which one is not easily awoken).
• adj. Immersed, submerged (in).
• adj. Muddy; boggy; sandy; said of roads.
• adv. Deeply.
• n. (literary, with "the") The deep part of a lake, sea, etc.
• n. (rare) A deep shade of colour.
• n. (US, rare) The profound part of a problem.
• n. (with "the") The sea, the ocean.
• n. (cricket) A fielding position near the boundary.

inaudible

• adj. Unable to be heard or not loud enough to be heard.

profound

• adj. Descending far below the surface; opening or reaching to great depth; deep.
• adj. Very deep; very serious.
• adj. Intellectually deep; entering far into subjects; reaching to the bottom of a matter, or of a branch of…
• adj. Characterized by intensity; deeply felt; pervading.
• adj. Bending low, exhibiting or expressing deep humility; lowly; submissive.
• n. (obsolete) The deep; the sea; the ocean.
• n. (obsolete) An abyss.
• v. (obsolete) To cause to sink deeply; to cause to dive or penetrate far down.
• v. (obsolete) To dive deeply; to penetrate.

silent

• adj. Free from sound or noise; absolutely still; perfectly quiet.
• adj. Not speaking; indisposed to talk; speechless; mute; taciturn; not loquacious; not talkative.
• adj. Keeping at rest; inactive; calm; undisturbed.
• adj. (pronunciation) Not pronounced; having no sound; quiescent.
• adj. Having no effect; not operating; inefficient.
• adj. (technology) Without audio capability.
• adj. Hidden, unseen.
• adj. Of an edit or change to a text, not explicitly acknowledged.
• adj. Not implying significant modifications which would affect a peptide sequence.
• adj. Undiagnosed or undetected because of an absence of symptoms.
• n. (uncountable) That which is silent; a time of silence.
• n. A silent movie.

unfathomed

• adj. Of unknown depth.
• adj. Not explored or understood.

unhearable

• adj. That cannot be heard.

unplumbed

• adj. Not measured for depth, as if with a plumb.