again and again Antonyms

could never happen on and off every so often every once in a while episodically at no time at intervals any more by fits and starts on occasion now and then once in a blue moon every now and then can never happen by no chance only now and then on no occasion on rare occasions not often almost never hardly ever at the greek calends certainly not now and again from time to time periodically occasionally irregularly interruptedly intermittently infrequently inconsistently hardly desultorily chaotically randomly rarely at times at random unexpectedly by chance unoften temporarily sporadically sometimes seldom scarcely accidentally