Learner's definition of IMPULSE
1 : a sudden strong desire to do something
◊ To do something on (an) impulse or on a sudden impulse is to do it suddenly and without thinking about it first.
An impulse buy/purchase is something that is bought on impulse and that usually is not really needed.
— often followed by to + verb
Impulse buying is the act or practice of buying things on impulse.
2 technical : a small amount of energy that moves from one area to another