Omnisexual is synonymous to pansexual. One's just a reference to promiscuity of the certain divine half-goat and the other isn't.
Anonymous

quartz-poker-deactivated2018120:

Pansexual: Fancy term for bisexual, but used by pansexuals to mean “Able to love anything.” And the word “Pan” in it is used to mean “All”, it’s not a reference to Pan the greek god. Think “Pan-America” for an etymological equivalent.

Omnisexual: Not only willing to love anything that moves, but actively pursuing it (if we go by the examples set in fiction).

Pansexual is NOT in fact a fancy term for bisexual. Bisexual people are only into girls and guys whereas pan people, gender doesn’t matter.