[on the wrong track] {adv. phr.} Lost; pursuing the wrong lead. […]

[on time] {adv.} or {adj. phr.} 1. At the time arranged; […]

[on top] {adv.} or {adj. phr.}, {informal} In the lead; with […]

[on trial] {adv.} or {adj. phr.} 1. For testing or trying […]

[once and for all] {adv. phr.} 1. One time and never […]

[once in a blue moon] {adv. phr.} Very rarely; very seldom; […]

[once in a while] {adv. phr.} Not often; not regularly; sometimes; […]

[once upon a time] {adv. phr.} Sometime before now, long ago. […]

[one of these days] or [some of these days] {adv. phr.} […]

[one's head off] {adv.} Loud or excessively. "I laughed my head […]