The definition of a cousin is the child of your aunt and/or uncle.(noun)
An example of a cousin is the baby born to your mother's sister.
See cousin in Webster's New World College Dictionary
Origin: ME cosin < OFr < L consobrinus, orig., child of a mother's sister, also cousin, relation < com-, with + sobrinus, cousin on the mother's side < base of soror, sister
See cousin in American Heritage Dictionary 4
Origin: Middle English cosin, a relative
Origin: , from Old French
Origin: , from Latin cōnsōbrīnus, cousin
Origin: : com-, com-
Origin: + sōbrīnus, cousin on the mother's side; see swesor- in Indo-European roots.
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