The Collaborative International Dictionary of English v.0.48:

Thunderer \Thun"der*er\, n.
   One who thunders; -- used especially as a translation of L.
   tonans, an epithet applied by the Romans to several of their
   gods, esp. to Jupiter.
   [1913 Webster]

         That dreadful oath which binds the Thunderer. --Pope.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Thunderer
    n 1: an epithet for Jupiter [syn: Jupiter Tonans, Thunderer]
    2: a noisemaker that makes a sound like thunder