How would you define "unbalanced forces"?

Answer 1

Unbalanced forces can be defined as forces that cause a change in motion or direction of an object. When two or more forces acting on an object are not equal in size or direction, they result in a net force, which can cause the object to accelerate, decelerate, or change direction. An object will continue to move with an unbalanced force until a balanced force is applied to it or until it meets with an opposing force.

Answer 2

any set of forces whose sum is not zero.

Answer 3

Correction:
An object will continue to ACCELERATE with an unbalanced force until a balanced force is applied to it or until it meets with an opposing force.