[nutcase] {n.} An insane person.

[nuthouse] {n.} A lunatic asylum.

[nutmeg] {v.} In association football, to pass the ball between an […]

[nuts or nutty] {adj.} Crazy or insane.

[nutter] {n.} Insane person.

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

[off one's head (or out of one's head)] {adj.} Mad or […]

[off one's nut] {adj.} Crazy or foolish.

[off the hook] {adj.} Free from obligation or danger.

[oik] {n.} Someone of a low social standing (derogatory).