white whales

Noun

white whale (plural white whales)

1. Synonym of beluga (“the beluga whale, Delphinapterus leucas, a cetacean found in the Arctic Ocean”)
   • The English called the beluga the "white whale", a name often still used (and not to be confused with the white whale of Moby-Dick, which was an albino sperm whale).2007, Nancy Lord, “Prologue”, in Beluga Days: Tracking the Endangered White Whale, pages 22–23

   Synonyms:

   melonhead, sea canary, beluga

2. Any whale of the family Monodontidae, which comprises the beluga whales and narwhals (Monodon monoceros), and some extinct species.
3. (figuratively) An obsession, a monomania.
   • 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
4. (figuratively, collectible card games) A printing plate, used to manufacture a particular sports card, that is then issued as a collectible itself.