Definitions of muster:

• noun:   a gathering of military personnel for duty

  Example: "He was thrown in the brig for missing muster"

• noun:   compulsory military service
• verb:   call to duty, military service, jury duty, etc.
• verb:   gather or bring together

  Example: "Muster the courage to do something"

• name:  A surname (very rare: popularity rank in the U.S.: #55296)