on and off

不时；断断续续地，间歇地

omission, omit, omni-, omnibus, omnipotence, omnipotent, omnipresent, omniscience, omniscient, omnivorous, on, on (the/an) average, on a large scale, on a level with, on a river, on a small scale, on a weekly (daily basis), on account of, on an average, on an even keel, on average, on balance, on behalf of, on board, on business, on condition that, on credit, on cue, on diet, on display, on duty, on earth, on end, on file, on fire, on foot, on guard, on hand, on instalments, on instinct,