[obey the call of nature] See: [ANSWER THE CALL OF NATURE].

[OBTW] "Oh, by the way"

[occasion] See: [ON OCCASION].

[occupy oneself] {v. phr.} To make oneself busy with. * /Having […]

[odd jobs] {n. phr.} Work that is not steady or regular […]

[oddball] {n.}, {slang}, {informal} An eccentric person; one who doesn't act […]

[odds] See: [BY ALL ODDS].

[odds and ends] {n. phr.} Miscellaneous items; remnants. * /After the […]

[odds and sods] {n.} Substitute for '[odds and ends]'. Miscellaneous items […]

[odds are against] {v. phr.} The likelihood of success is not […]