if someone or something is an unknown quantity, you do not know much about them or what effect they will have in the future.

Turner may do well in the election, though he is an unknown quantity as a campaigner.

The new computer system is still an unknown quantity for our department.

• throw on
• throw on mercy
• throw on someone's mercy
• throw on something
• throw on the scrap heap
• throw open something to
• throw open something to someone
• throw open something to something
• throw open to
• throw open to someone
• throw open to something
• throw out
• throw out something
• throw out the baby with the bath water
• throw someone a curve
• throw someone a curve ball
• throw someone for a loop
• throw someone in at the deep end
• throw someone into a spin
• throw someone into a tizz
• throw someone into a tizzy
• throw someone off balance
• throw someone off the scent
• throw someone on the scrap heap
• throw someone out