either of two fleshy folds of tissue that surround the mouth and play a role in speaking
"She carefully applied red lipstick to her lip while looking into the mirror."
(botany) either of the two parts of a bilabiate corolla or calyx
"The delicate lip of the orchid's upper petal curves inward to shelter the pollen."
either the outer margin or the inner margin of the aperture of a gastropod's shell
"The collector carefully measured the lip thickness on both the outer and inner margins of the ancient snail's shell."
Either of the two fleshy protrusions around the opening of the mouth.
"Scientists are studying the formation of LIPs to understand how massive volcanic eruptions affect global climate."
Abbreviation of large igneous province.
In plain English: A lip is either your mouth's edge that moves when you talk and eat, or an outer covering of something like a cup rim.
"She smiled and showed her white teeth between her lips."
Usage: Use this word when referring specifically to either of the two muscular folds surrounding your mouth, distinct from cheeks or gums. It is often confused with "lips" in plural form only when discussing both sides simultaneously, but singular usage remains correct for individual parts.
To touch or grasp with the lips; to kiss; to lap the lips against (something).
"The cat dipped its head down to lap milk from the bowl, touching the liquid directly with its lips."
In plain English: To lip means to speak by moving your mouth without making any sound.
"The dog began to lip forward when he saw his owner walking toward him with treats in hand."
The word "lip" comes from Old English and has always meant the fleshy part of the mouth. Its ultimate origin is a root meaning to hang loosely or droop.