any of various long-tailed primates (excluding the prosimians)
"The researcher observed a group of macaques swinging through the canopy, confirming they were monkeys rather than prosimians."
Any member of the clade Simiiformes not also of the clade Hominoidea containing humans and apes, from which they are usually, but not universally, distinguished by smaller size, a tail, and cheek pouches.
"The researcher spent hours observing how the monkey used its long tail for balance while gathering fruit in the canopy."
In plain English: A monkey is an animal with long arms and no tail that lives in trees.
"The curious monkey swung from branch to branch in the jungle."
Usage: Use "monkey" as a noun to refer specifically to Old World monkeys like baboons or macaques, distinguishing them from apes. As a verb, it means to interfere playfully with something rather than simply playing around.
do random, unplanned work or activities or spend time idly
"The old lady is usually mucking about in her little house"
To meddle; to mess (with).
"Stop monkeying around and finish your homework."
In plain English: To monkey around means to play around, act silly, or waste time instead of doing something serious.
"The toddler began to monkey around with his father's tools on the workbench."
The ninth of the 12-year cycle of animals which appear in the Chinese zodiac related to the Chinese calendar.
"In the Chinese zodiac, people born in 1980 are considered monkeys because it is the ninth animal in the twelve-year cycle."
The origin of "monkey" is uncertain but may come from either an English blend of monk and -ey or a borrowing from Middle Low German. If it entered via French terms like monne, these words originally referred to the specific name Monnekin given to a character in medieval stories before becoming the general term for the animal.