Source : Webster's Revised Unabridged Dictionary (1913)

Agnus \Ag"nus\, n.; pl. E. {Agnuses}; L. {Agni}. [L., a lamb.]
   Agnus Dei.

Source : WordNet®

Agni
     n : (Sanskrit) god of fire in ancient and traditional India; one
         of the three chief deities of the Vedas