[off a duck's back] See: [LIKE WATER OFF A DUCK'S BACK]

[off and on] also [on and off] {adv.} Not regularly; occasionally; […]

[off balance] {adj. phr.} 1. Not in balance; not able to […]

[off base] {adj. phr.}, {informal} Not agreeing with fact; wrong. * […]

[off center] {adv. phr.} Not exactly in the middle. * /Mary […]

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

[off duty] {adj.} Not supposed to be at work; having free […]

[off feed] or [off one's feed] {adj. phr.}, {informal} Not feeling […]

[off guard] {adj.} In a careless attitude; not alert to coming […]

[off in a flash] See: [IN A FLASH].