The phrase "variable one" refers to a value or thing that can change or vary. It is often used in math or programming to represent an unknown quantity that can be assigned different values. Full definition
Whole life is the simplest and least risky version because its cash value portion is a simple savings account, whereas the other three all incorporate an investment product with variable returns. (policygenius.com)
It also goes by the names «variable premium life» or «flexible premium life». (choicemutual.com)
Banks love predictable cash flows — hence, the lower rate for variable rate loans. (studentloancoach.info)