- matter of opinion
- (video games) Master of Orion.
- (video games) MUD, Object Oriented.
- (dated, postal) Money Order Office.
1893, George A. de M. Edwin Dagg, "Devia Hibernia" : the road and route guide for Ireland of the Royal Irish Constabulary, page vi:
- […] (3) the nature of the Postal business accommodation supplied by the local Post-Office—thus, PO (Post-Office), SB (Savings Bank), MOO (Money Order Office), or, if there be no PO, the name and distance of the nearest PO […]
1993, Christopher Browne, Getting the Message: The Story of the British Post Office, page 88:
- It was to help solve a serious problem – mice. For the little vermin were chewing letters containing banknotes and postal orders, especially at the Money Order Office (MOO).
- (astronomy) Abbreviation of massive overdense object.