O

Acronym	Definition
O	Oh
O	Outstanding
O	Oxygen
O	Officer (military)
O	Operator (telephone)
O	Octal
O	Official
O	Organization
O	Outdoor
O	Orange
O	Out (baseball)
O	Operations
O	New Orleans, Louisiana (mint mark)
O	Oscar (aviation letter code)
O	Output
O	Offensive (Catholic movie rating)
O	Orgasm
O	Ortho (Benzene)
O	Hug(s)
O	Operational
O	Observer
O	Organizational
O	Order of Magnitude (computer algorithms)
O	Oxide
O	Otis (Redding)
O	Immediate (logging abbreviation)
O	Odin
O	Ohm
O	Oscar Robertson (former NBA player)
O	Oprah (magazine)
O	Ouest (French: west)
O	Othello
O	Observation (US military aircraft designation; as in O-1)
O	Orthogonal (mathematics)
O	Obstacle (course)
O	Defensive Team (sports/coaching)
O	Omit
O	Outliers
O	Omikron (German: Omicron; 15th letter of the Greek alphabet)
O	Oberst (German)
O	Over to You (radio communications)
O	Morally Offensive (Catholic movie rating)
O	Origin Server (Internet)
O	Organized Naval Reserve (US Navy)
O	Optional Levels (board test for high schoolers, UK)
O	Officer of Operations (US Navy)
O	Ohne Hauch (antigen)
O	Ost/Osten (German: East)
O	Measurement of Cloud Cover
O	Toy train railroad gauge (2 1/4 inch wide, originated in Germany)