Tonic

a. [Fr. tonique, It. & Sp. tonico, Gr. τονικός.] See TONE.

1Sense 1. Of, or relating to, tones or sounds.

2Sense 2. Extensive, or causing extension, as muscular action. [Obs.] Browne.

3Sense 3. Increasing tension; hence, increasing strength; as, tonic power.

4Sense 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.

n. [Fr. tonique, N. Lat. tonicum.] 1. (Med.) A medicine that increases the strength, and gives vigor of action to the system. 2. (Mus.) The key-tone, or first tone of the scale.