X factor
X factor · X factors
An unknown or hard-to-define influenceAn unknown or hard-to-define influence; a factor with unknown or unforeseeable consequences.
Meaning
4 senses(idiomatic)An unknown or hard-to-define influence; a factor with unknown or unforeseeable consequences.
(idiomatic)A special talent, ability or quality or its indefinable cause.
Prothrombinase.
The proportionality constant which converts CO emission line brightness to molecular hydrogen mass.