Learner's definition of WHIM
: a sudden wish, desire, decision, etc.
the whims of fashion
It's hard to predict voters' whims.
Her husband tries to satisfy her every whim. [=make her happy by doing everything that she wants]
He quit his job on a whim. [=because of a sudden decision]
The shop is only open at the whim of the owner. [=the shop is only open when the owner wants it to be open]