-ˌtōrē, -ˌtȯr-, -ri adjective
Etymology: Medieval Latin supererogatorius, from supererogatus + Latin -orius -ory
1.
a. : of, relating to, or characterized by supererogation
b. : observed or performed to an extent not enjoined or required
supererogatory acts
2. : that can be dispensed with : superfluous , nonessential
metaphors … are pleasurable accessories … which are supererogatory when one comes down to the business of understanding what is said — R.M.Weaver