Source : Webster's Revised Unabridged Dictionary (1913)

Trinal \Tri"nal\, a. [L. trinus triple, trini three each, fr.
   tres, tria, three. See {Three}, and cf. {Trine}, a. & n.,
   {Tern}, a.]
   Threefold. ``Trinal unity.'' --Milton.

         In their trinal triplicities on high.    --Spenser.