ETYM Etymology uncertain. Mr. J. H. Trumbull finds the origin of caucus in the North American Indian word cawcawwassough or caú cau-as'u one who urges or pushes on, a promoter. Related to citation for an early use of the word caucus.
(Irregular plural: caucuses).
A closed political meeting.
Small powerful committee, especially in political party; meeting of such committee.
In the US, a closed meeting of regular party members; for example, to choose a candidate for office. The term was originally used in the 18th century in Boston, Massachusetts.

To meet to select a candidate or promote a policy.