One collaterally related more remotely than a brother or sister; especially, the son or daughter of an uncle or aunt.
In colonial times, it most often meant nephew or niece. In the broader context, it could also mean any familial relationship, blood or otherwise,( except father, mother, brother, sister), or the contemporary meaning of a child of one's aunt or uncle. Modern usage includes qualifiers such as first, second, third, and once removed, twice removed, etc. First cousin is what most people commonly call their cousins, that is an aunt's or uncle's child. Second cousin is a child of the first cousin, as is a first cousin once removed. Similarly, a first cousin twice removed and a third cousin denote the same member of the family--a first cousin's grandchild.
the child of your aunt or uncle
a descendant of a brother or sister of your father or mother and does not qualify under the relationship test
a grandchild (or further descent) of one's grandparent (or further ascendant)
a person collaterally related more remotely than a brother or sister
a ready-made friend for life
a relative with whom you share a set of grandparents
1] a child of one's aunt or uncle; also called first cousin;  a relative descended from a common ancestor, such as a grandparent, by two or more steps in a diverging line;  a relative by blood or marriage; a kinsman or kinswoman;  a member of a kindred group or country
A first cousin once removed is the child of a person's first cousin. A second cousin twice removed is the grandchild of a person's second cousin.
A relative descended from a common ancestor, but not a brother or sister
child of an aunt or uncle; in earlier times a kinsman, close relative, or friend.
used for any relation. Mr Bennet refers to Mr Collins, his nephew, as 'cousin'
Person with whom one has ancestors in common
In genealogy, a cousin is a relative with whom one shares a common ancestor, however even in the most general sense the term does not apply to the relationships one has with one's ancestors (mother, father, grandparent), or the siblings of one's ancestors (aunt, uncle), nor to the relationships one has with one's descendants (child, grandchild), or one's siblings (brother, sister) nor to the relationships one has with the descendants of one's siblings (niece, nephew) because more specific terms are used to describe such relationships.