Open English Wordnet
Nouns
(n)smoothnessa texture without roughness; smooth to the touch“admiring the slim smoothness of her thighs”, “some artists prefer the smoothness of a board”
(n)eloquence, fluency, smoothnesspowerful and effective language“his eloquence attracted a large congregation”, “fluency in spoken and written English is essential”, “his oily smoothness concealed his guilt from the police”
(n)suavity, suaveness, blandness, smoothnessthe quality of being bland and gracious or ingratiating in manner
(n)smoothnessthe quality of having a level and even surface“the water was a glassy smoothness”, “the weather system of the Pacific is determined by the uninterrupted smoothness of the ocean”
(n)smoothnessthe quality of being free from errors or interruptions“the five-speed manual gearbox is smoothness personified”