Real Dictionary

muster
verb: If you muster something such as support, strength, or energy, you gather as much of it as you can in order to do something.
verb: When soldiers muster or are mustered, they gather together in one place in order to take part in a military action.

muster in American English
to assemble or summon (troops, etc.), as for inspection, roll call, or service
intransitive verb: to assemble for inspection, service, etc., as troops or forces
transitive verb: to assemble (troops, a ship's crew, etc.), as for battle, display, inspection, orders, or discharge

muster in British English
verb: to call together (numbers of men) for duty, inspection, etc, or (of men) to assemble in this way