soundly Definition

sound²
adj

1. Not damaged or injured; in good condition; healthy.

Example: The kitten was found safe and sound
Thesaurus: healthy, hearty, well, robust, fit, vigorous, hale; firm, solid, stable, sturdy.
2a. Sensible; well-founded; reliable;

Example: sound advice
Example: a sound investment
Thesaurus: sensible, reasonable, rational, prudent, judicious, wise, level-headed, logical; dependable, loyal, true, faithful, reliable, trustworthy, responsible, reputable.
2b. Said of an argument, opinion, etc: well researched or thought through, logical and convincing.
3. Acceptable or approved of.

Thesaurus: sanctioned, established, allowed, proper, well-founded, fair, valid, legal, correct, orthodox.
4. Severe, hard or thorough.

Example: a sound spanking
5. Said of sleep: deep and undisturbed.

adverb

1. Deeply.

Example: sound asleep

Derivative: soundly
adverb

Derivative: soundness
noun

Etymology: Anglo-Saxon gesund.