An unpredictable person or thing, as in We don't know how the new pitcher will dohe's an unknown quantity. This expression comes from algebra, where it signifies an unknown numerical value. Its figurative use dates from the mid-1800s.
|1.||a factor in a given situation whose bearing and importance is not apparent; "I don't know what the new man will do; he's still an unknown quantity"|
|2.||a variable whose values are solutions of an equation [syn: unknown]|