Other forms: smoother, smoothing, smoothed, smoothest, smooths
Smooth means completely even to the touch, with no bumps or roughness. A smooth surface, smooth skin, sand it smooth.
It extends to movement — a smooth ride, a smooth landing — and to processes that go without trouble: a smooth handover, everything went smoothly. Applied to a person, smooth means charming in a way that is not quite trusted: a smooth operator. Note the th sound, which is voiced, and the verb smooth, which means to make even: smooth it down, smooth things over. The noun smoothie is a thick blended drink.
1adjectivesmoothEven to the touch, with no bumps.
“The stone is worn completely smooth.”
2adjectivehappeningHappening without difficulty.
“It was a smooth handover and nobody noticed.”
3verbverbTo make something even.
“Smooth the paper down before you tape it.”
Too few real examples of this word to estimate which sense is commonest.
smooth is a quality of evenness.
Old English smethe has no clear relatives outside English, which is unusual for so basic a word. The spelling with -oo- settled late and the pronunciation kept the voiced th, which is why smooth and soothe rhyme.
Middle English
smothe
English, today
smooth
From Middle English smothe. From Middle English smothe, smethe, from Old English smēþe, smōþ, both from Proto-West Germanic smanþī, of unknown origin. Cognate with Scots smuith (“smooth”), stq smoud (“smooth”), Low German smood and smödig (“smooth, malleable, ductile”), Dutch smeuïg (“smooth”) (from earlier smeudig).
Etymology from Wiktionary, CC BY-SA