unknown quantity

Idioms and Phrases

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.

Example Sentences

But when he quit, that number jumped to 9%, reflecting the fact that Harris was an unknown quantity to many Americans.

From Salon

While most analysts believe Beijing does not have a favourite in this race for the White House, many would agree that Kamala Harris is an unknown quantity to Chinese people and the country’s leaders.

From BBC

Newcastle are still a bit of an unknown quantity for me because I can't say I've been particularly impressed by them so far.

From BBC

Kamala Harris was an unknown quantity to leaders here and she still is, even after the debate.

From BBC

They will be an unknown quantity with very little Premier League experience in their squad, and an exciting up-and-coming manager in McKenna.

From BBC

Related Words

• also-ran
• long shot
• sleeper
• underdog