The descriptive term used to denote the manner in which a rod flexes when loaded with the flyline. You should choose a *progressive* actioned rod. This rod flexes at the tip for short casts, but can be flexed deeply for longer casts. Tip actioned rods and through actioned rods are the alternatives BTW.
Action could also be used as a descriptive term with regards to some flies as in "wiggly-tail flies have an unusual interesting action".