be an unknown quantity

be an unknown quantity

To be unpredictable and thus difficult to anticipate. We're still revising our new product, so its potential success is an unknown quantity as yet. This is her first year teaching, so her ability to connect with her students is still something of an unknown quantity. I missed that guy's audition, so he's still an unknown quantity to me as a guitar player.
See also: an, quantity, unknown
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.
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