Something that causes and encourages a given response
To stir to action or feeling
On the spur of the moment you pick up the suitcases, put them in your trunk, and drive off.
I did it on the spur of the moment.
On the spur of the moment he telephoned her.
"I have a friend who's an attorney," Dean said, on the spur of the moment.
We all do something on the spur of the moment once in awhile.