[nut case] {n. phr.} A very silly, crazy, or foolish person. […]

[nuts and bolts of] {n. phr.} The basic facts or important […]

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

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

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

[off day] {n. phr.} A period when one is not functioning […]

[offshoot] {n.} A derivative; a side product. * /The discovery of […]

[old boy] or [old chap] {n.}, {chiefly British} One of the […]

[old boy network] {n. phr.} A system whereby men who went […]

[old college try] {n. phr.} An attempt to win a favor […]