The Collaborative International Dictionary of English v.0.48:

Mithra \Mi"thra\, Mithras \Mi"thras\, prop. n. [L., from Gr. ?.]
   The sun god of the ancient Persians; the god of light and
   truth.
   [1913 Webster] mithraic

WordNet (r) 3.0 (2006):

Mithras
    n 1: ancient Persian god of light and truth; sun god [syn:
         Mithras, Mithra]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "Mithras":
   Agdistis, Amor, Aphrodite, Apollo, Apollon, Ares, Artemis, Ate,
   Athena, Bacchus, Ceres, Cora, Cronus, Cupid, Cybele, Demeter,
   Despoina, Diana, Dionysus, Dis, Eros, Gaea, Gaia, Ge, Great Mother,
   Hades, Helios, Hephaestus, Hera, Here, Hermes, Hestia, Hymen,
   Hyperion, Jove, Juno, Jupiter, Jupiter Fidius, Jupiter Fulgur,
   Jupiter Optimus Maximus, Jupiter Pluvius, Jupiter Tonans, Kore,
   Kronos, Magna Mater, Mars, Mercury, Minerva, Momus, Neptune, Nike,
   Olympians, Olympic gods, Ops, Orcus, Persephassa, Persephone,
   Phoebus, Phoebus Apollo, Pluto, Poseidon, Proserpina, Proserpine,
   Rhea, Saturn, Tellus, Venus, Vesta, Vulcan, Zeus