Real Dictionary

gibbon
countable noun: A gibbon is an ape with very long arms and no tail that lives in southern Asia.

Gibbon in American English
any of a family (Hylobatidae) of small, slender, long-armed, tree-dwelling, anthropoid apes of India, S China, and the East Indies
Edward1737-94; Eng. historian
noun: any small, slender, long-armed arboreal anthropoid ape of the genus Hylobates, of the East Indies and southern Asia: all gibbon species are reduced in number and some are very rare

gibbon in British English
noun: any small agile arboreal anthropoid ape of the genus Hylobates, inhabiting forests in S Asia
noun: Edward. 1737–94, English historian; author of The History of the Decline and Fall of the Roman Empire (1776–88), controversial in its historical criticism of Christianity