Exact historical dictionary sense
Prime in Webster's 1913 dictionary
The 1913 record labels prime as adjective. Its source-bounded etymology and selected historical definition appear below.
[F., fr. L. primus first, a superl. corresponding to the compar. prior former. See Prior, a., Foremost, Former, and cf. Prim, a., Primary, Prince.]
Cross-verified historical senseIn Webster's Revised Unabridged Dictionary (1913), "prime" is labeled adjective. Its etymology is recorded as: "[F., fr. L. primus first, a superl. corresponding to the compar. prior former. See Prior, a., Foremost, Former, and cf. Prim, a., Primary, Prince.]" The selected historical definition says: "First in order of time; original; primeval; primitive; primary."