impellent

adj

1. Having the quality of being impelling.

   “an impellent force”

   “Hence, the excess of impellent force which was given to the piston, beyond what was absolutely requisite to overcome the resistances to its motion, was made available to prolong that motion, beyond the point at which the impellent force […]”

noun

1. An impelling power or force.

   “blind impellents and material conveyances”