Definition from Wiktionary, the free dictionary
From Latin ōrdō.
- A musical phrase constructed from one or more statements of one modal pattern and ending in a rest.
- (Roman Catholicism) A calendar which prescribes the Mass and office which is to be celebrated each day.
See also 
Derived terms 
- A methodical series, arrangement, or order; regular line, row, or series.
- A class, station, condition, rank.
- (military) A rank or line of soldiers; band, troop, company; command, captaincy.