|Origin:||monstrer, from Latin monstrare 'to show'|
1 [transitive] also muster up something
to get enough courage, confidence, support etc to do something, especially with difficulty [= summon (up)]
muster (up) the courage/confidence/energy etc to do something
Finally I mustered up the courage to ask her out.
Senator Newbolt has been trying to muster support for his proposals.
'It's going to be fine,' replied David, with as much confidence as he could muster.
2 [intransitive and transitive]
if soldiers muster, or if someone musters them, they come together in a group [= gather]:
In April 1185, he began to muster an army.