Definition of "white whale"

Synonym of beluga (“the beluga whale (Delphinapterus leucas), a cetacean found in the Arctic Ocean”)  quotations  examples

Any whale of the family Monodontidae, which comprises the beluga whales and narwhals (Monodon monoceros), and some extinct species.  examples

(figuratively)

1. An obsession, a monomania.  quotations  examples

   Quotations

   • No … no sapphires. It looks like Lester Velasquez was chasing his white whale. There never were any sapphires inside that diner.

     2008, Glen Inglis, Broken Heroes, page 228

   • For nearly four years, Snapchat has been Facebook’s white whale.

     2016 August 2, Mike Isaac, “Instagram takes a page from Snapchat, and takes aim at it, too”, in The New York Times‎

   • After being lofted into space by a Falcon Super Heavy, his next rocket, the Starship, will light out for the moon, land there, take off and return to Earth, with no stages expended on the lunar journey. This so-called single-stage-to-orbit model has been the white whale of rocket designers for generations.

     2021 December 13, Molly Ball, Jeffrey Kluger, Alejandro de la Garza, “Elon Musk: Person of the Year 2021”, in Time Magazine‎

2. (collectible card games) A printing plate, used to manufacture a particular sports card, that is then issued as a collectible itself.  examples