Definitions of caucus
a meeting of legislators who are members of the same political party to select candidates or decide policy; the members of such a body
The difference between a caucus and the primaries that most states favor is that to take part in a caucus you have to take part in person.
a meeting, in particular a meeting of people whose goal is political or organizational change
The caucus has a low turnout and is dominated by groups trying to draw attention to local issues such as farming and ethanol subsidies.
a term used in US presidential politics to describe the process of party members registering preferences for candidates or selecting convention delegates
The Iowa presidential caucus happens once every four years.