Tōn'ic1, a.
a. [Fr. tonique, It. & Sp. tonico, Gr. τονικός.] See TONE.
Sense 1. Of, or relating to, tones or sounds.
Sense 2. Extensive, or causing extension, as muscular action. [Obs.] Browne.
Sense 3. Increasing tension; hence, increasing strength; as, tonic power.
Sense 4. (Med.) Increasing strength, or the tone of the animal system; obviating the effects of debility, and restoring healthy functions.
Tonic spasm (Med.), a steady and continuous spastic contraction enduring for a comparatively long time. It is opposed to a clonic spasm, in which the muscular fibers contract and relax alternately in very quick succession.