sound

1 to measure the depth of (as a body of water) typically with a weighted line the pilot sounded the river to make sure we weren't in any danger of running aground Synonyms fathom, plumb Related Words gauge (also gage), scale, span; remeasure, replumb

2 to cast oneself head first into deep water a whale suddenly surfaced and then, just as suddenly, sounded Synonyms pitch, plunge, soundRelated Words dip, immerse, submerge; belly flop, plump, plunk (or plonk)Near Antonyms surface

range of hearing wandered off, out of her parents' sight and sound Synonyms hail, hearing, soundRelated Words volume; distance, sight

a narrow body of water between two land masses Long Island Sound is between Long Island, New York, and Connecticut Synonyms narrows, neck, sound, straitRelated Words arm, bay, gulf, inlet; roads, roadstead; reach, stretch

1 according to the rules of logic sound reasoning alone should tell you that the result is invalid Synonyms analytic (or analytical), coherent, consequent, good, rational, reasonable, sensible, logical, valid, well-founded, well-groundedRelated Words a posteriori, a priori, syllogistic; cognitive, empirical (also empiric); defendable, defensible, justifiable, maintainable, supportable, sustainable, tenableNear Antonyms casuistic (or casuistical), eristic (also eristical), fallacious, misleading, sophistic (or sophistical), specious; unarticulated; unscientific; absurd, cockeyed, crazy, daffy, fatuous, half-baked, half-witted, harebrained, insane, loony (also looney), mad, nonsensical, nutty, preposterous, simpleminded, stupid, weak-minded, witless; senseless, thoughtless; uncompelling, unconvincingAntonyms illegitimate, illogical, incoherent, inconsequent, inconsequential, invalid, irrational, unreasonable, unsound, weak

2 enjoying health and vigor the horse is getting along in years, but still perfectly sound Synonyms able-bodied, bouncing, fit, hale, hearty, robust, healthy, well, well-conditioned, whole, wholesomeRelated Words hard, hardy, iron, lusty, rugged, stalwart, strong, sturdy, tough; ambulatory, nondisabled, uncrippled; active, agile, chipper, lively, sprightful, sprightly, spry, vigorous, vital; blooming, clean-cut, flourishing, flush, prospering, thriving; all right, good, rightNear Antonyms decrepit, enfeebled, feeble, infirm, run-down, sickened, sickly, weak, weakened, weakly, worn-out; challenged, crippled, debilitated, differently abled, disabled, halt, incapacitated, lame; delicate, fragile, frail; emaciated, gaunt, haggard, malnourished, undernourished; afflicted, troubled; bad, poorlyAntonyms ailing, diseased, ill, sick, unfit, unhealthy, unsound, unwell

3 marked by the ability to withstand stress without structural damage or distortion the shed looks flimsy, but it's actually surprisingly sound Synonyms bombproof, fast, firm, stable, stalwart, strong, sturdyRelated Words dependable, durable, reliable; infrangible, irrefragable, unbreakable; beefy, solid; cohesive, toughNear Antonyms infirm, insecure, weak; shaky, tottering, tottery, unbalanced, wobbly (also wabbly); unsubstantialAntonyms rickety, unsound, unstable, unsteady