Initialism of occupational health and safety.

Expression of surprise. / Expression of wonder, amazement, or awe. / Expression of understanding, affirmation, recognition, or realization. / A word to precede an offhand or annoyed remark.

An utterance of oh; a spoken expression of surprise, acknowledgement, etc.

(intransitive) To utter the interjection oh; to express surprise, etc.

the letter O, o (more commonly spelled o)

the digit 0 (especially in representations of speech)

(organic chemistry) A hydroxyl, or alcohol, functional group. / (inorganic chemistry) A hydroxide radical, or hydroxyl group.

An exclamation or expression of alarm, concern, or resentment about a problem or error.

(sports) A game or time period in which a player did not manage to sustain a particular attainment. / (baseball) An instance in which a player did not get a hit in a game.

plural of oh