2 example sentences using onomastic.
Onomastic used in a sentence
Onomastic in a sentence as an adjective
I mean, "onomastics" really should win simply for already being the established term.
Caution: etymologically-oriented answers generally miss important nominological / nymological / onomatological / onomastic foundations.
Onomastic definitions
adjective
of or related to onomastics; "he published a collection of his onomastic essays"