on the spur of the moment
1．in a sudden impulse一时高兴或冲动
He had not planned to take the trip； he just went on the spur of the moment．他事先没有计划这趟旅行，只是一时高兴就走了。
I've accepted the offer of a job abroad． I decided on the spur of the moment to go．我已接受了国外的工作并决定马上就走。
He acts on the spur of the moment．他凭一时冲动行事。
2． on the spot当场；即席
He can invent any number of excuses on the spur of the moment．
他能当场诌出许多托辞。
Though quite unprepared，he was nevertheless able to sing a folk songon the spur of the moment．尽管毫无准备，他还是能即席演唱一首民歌。