Longman Dictionary of Contemporary English - whim

~ n a sudden feeling that you would like to do something or have something, especially when there is no particularly important or good reason  (on a whim (=because of a whim))  (I went to visit her on a whim. | at the whim of)  (The palace decor kept changing at the whim of the princess. | a passing whim (=one that will soon be forgotten) | sb's every whim)  (I was spoiled. My every whim was catered to.)