This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

ad. In a quiet manner, without any noise.

In a noiseless manner; without noise; silently.

ad. without a sound

"Subconsciously he called noiselessly upon the God that had sustained him and, divided between apprehension and the increasing lust to kill, his lips held the form in which they had pronounced that impressive name."

noisily   

noiseless    noisily    noisy    noise   

silently    inaudibly    quietly   

standard-sized    towalk    runni    taxpaying    plosive