Definition - A sound made with one or both lips, e.g. the [f] in filter.

1. When both lips are used, the sound is called a bilabial, e.g. the [p] in popcorn.

Etymology -
The word derives from the Latin labium, lip.

Oxford English Dictionary -
Its first citation is from 1594:
"The Hebrewes name their letters, some gutturall…; others dentall…; & so they call others, labiall, that is letters of the lips."
(T. B. La Primaud. Fr. Acad. ii. 87)

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