1. Subordinate or subsidiary action, as in the plot of a play or poem.
1697. Dryden, Æneis, Ded. ¶ 1. The least and most trivial episodes, or under-actions, which are interwoven in it, are parts either necessary or convenient to carry on the main design.
2. Insufficient or defective action; less than normal activity.
1887. Buck’s Handbk. Med. Sci., IV. 656. Correction of underaction and overaction of muscles, nerves, and their central reflex apparatus.
