noun
impulse
IM-puls/ˈɪmpʌls/
A sudden urge to do something.
The shopper reaches for a treat on impulse.

Etymology
A physical push became an inner stimulus that suddenly presses someone toward action.
More examples
- He resists the impulse to interrupt.
- On impulse, she takes a different route home.
Forms
impulse
Similar words
- urge
- A strong desire that need not be sudden.
- whim
- A passing wish, often with little serious purpose.