white whale

a.k.a. chasing a white whale or chasing white whale

Slang for relentlessly or obsessively pursuing an object that's difficult to achieve, as in "She's still doing screenwriting? Yep, that's her white whale." It usually implies a lack of regard for one's own safety and the safety of others, a chase that you'll never win, and some sort of tragic ending.

Historical perspective: It comes from the 1851 novel Moby Dick, by Herman Melville, in which Captain Ahab is obsessed with finding the whale who injured him on a previous voyage.

See also : pet shaming  
NetLingo Classification: Online Jargon