Porphyritic \Por`phy*rit"ic\, a. [Cf. F. porphyritique.]

(Min.) Relating to, or resembling, porphyry, that is, characterized by the presence of distinct crystals, as of feldspar, quartz, or augite, in a relatively fine-grained base, often aphanitic or cryptocrystalline.

Source: Webster's Revised Unabridged Dictionary (1913)