Source : Webster's Revised Unabridged Dictionary (1913)

Megalesian \Meg`a*le"sian\, a. [L. Megalesius, fr. Gr. Mega`lh
   the Great, a surname of Cybele, the Magna Mater.]
   Pertaining to, or in honor of, Cybele; as, the Megalesian
   games at Rome.