from Wiktionary, Creative Commons Attribution/Share-Alike License
- v. to "be a man about it"; to do the things a good man is traditionally expected to do, such as: taking responsibility for the consequences of one's actions; displaying bravery or toughness in the face of adversity; providing for one's family, etc.
- v. (of military personnel in a unit) to assemble, each person manning (attending to) his station, prepared for departure of an aircraft, ship, etc.
- v. (of personnel, industrial, etc.) to staff adequately; to staff up; to successfully fill all needed labor positions.
- v. to vigorously guard the opponent to which one is assigned
man + up, with influence from own up, buck up. Used frequently in military circles. (Wiktionary)