An odd or fanciful or capricious idea. Synonyms:notion, whim, whimsy."He had a whimsy about flying to the moon" , "Whimsy can be humorous to someone with time to enjoy it"
... the "Autocrat", who has moved always with reform, if not always with reformers, and whose protest against bigotry is as searching as it is sparkling. Not only has his ear been quick to detect the hum of Mr. Honeythunder's loud appeal, but his eye to catch the often ludicrous aspect of honest whimsey. During all the early years of his literary career he flew his flashing darts at all the "isms", and he fell under the doubt and censure of those earnest children of the time whom the gay and clever sceptics derided as apostles of the newness. When Holmes ... — Literary and Social Essays • George William Curtis