An unpredictable person or thing, as in We don't know how the new pitcher will do—he's an unknown quantity. This expression comes from algebra, where it signifies an unknown numerical value. Its figurative use dates from the mid-1800s.
THE SEPTEMBER WORD OF THE DAY QUIZ HAS ARRIVED!
Go ahead, test your mental legerity to see how many words you remember from last month!
Question 1 of 10
Which definition best describes “spang”?
Words nearby unknown quantity
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.