occasionaladj.偶然的；临时的；不时的occasional irregularity偶然异常occasional fatal trauma偶然的致命伤occasional regeneration偶然再生occasional transmission非经常传输occasional thunderstorm间中有雷暴occasional insemination偶然授精occasional moulding pit通气造型坑occasional premature beat偶发早搏occasional parthenogenesis偶发性单性生殖occasional monograph series不定期出版的专题丛刊