a sudden desire; "he bought it on an impulse"

A sudden turn or start of the mind; a temporary eccentricity; a freak; a fancy; a capricious notion; a humor; a caprice.

an odd or fanciful or capricious idea; "the theatrical notion of disguise is associated with disaster in his stories"; "he had a whimsy about flying to the moon"; "whimsy can be humorous to someone with time to enjoy it"

a capricious or eccentric and often sudden idea or turn of the mind, and "it" is a pronoun used to describe a group of individuals or things, or an abstract entity

a last minute, impulsive decision that you act on