The Collaborative International Dictionary
Tithonic
Tithonic \Ti*thon"ic\, a. [L. Tithonius belonging to Tithonus, the consort of Aurora, Gr. ?.] Of, pertaining to, or denoting, those rays of light which produce chemical effects; actinic. [R.]
Wiktionary
tithonic
a. Of, relating to, or denoting those rays of light which produce chemical effects; actinic.