unknown quantity

Definitions

1. 1

   A person or thing whose nature or value is a mystery.

   • Whatever he had learned of himself was here of no avail. He was an unknown quantity.
   • . . . the Evening Post of this city to refer to him recently as "the young Belgian painter," and to the general public he is an unknown quantity.
   • The big French diesel is something of an unknown quantity, whereas many French-built electric locomotives developing 3,000 h.p. and more have been well proved in service.
2. 2

   Used other than figuratively or idiomatically

   Used other than figuratively or idiomatically: see unknown, quantity.

   • Many of the applications of mathematics require that you identify an unknown quantity, assign a variable to that quantity, and then attempt to express another unknown quantity in terms of that variable.
   • So promising was the Skunk Works' stealth cruise missile offering, the USAF ordered an unknown quantity of these missiles under a highly classified program dubbed Senior Prom.

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