1(In some US states) a meeting at which local members of a political party register their preference among candidates running for office or select delegates to attend a convention:Hawaii holds its nominating caucuses next Tuesdayhe stumbled through the Iowa caucuses and the New Hampshire primary
2A conference of members of a legislative body who belong to a particular party or faction:Mr Kerry attended the morning caucus in the Old Senate Chamber where his fellow Democrats selected the new minority leadership
2The members of a legislative body who belong to a particular party or faction, considered as a group:she is renowned for her ability to unite her caucus
2.1An informal group composed of legislators who have shared concerns or interests:a member of the Congressional Black Caucusthe Knesset’s Christian allies caucus
A group within an organization or political party which meets independently to discuss strategy or tactics:up to fifty caucuses met daily on conference grounds to discuss lobbying strategieshe was forced out by a hard-left caucus which had taken over his constituency party
1Hold or form a legislative caucus:Republicans briefly caucusedthere is one Independent who caucuses with the Democrats
1.1(Of a voter) attend an electoral caucus, especially on behalf of a particular candidate:more than half of those young people that caucused yesterday caucused for Barack Obama
Origin
mid 18th century: perhaps from Algonquian cau’-cau’-as’u ‘adviser’.
How my heart sings 