The Collaborative International Dictionary of English v.0.48:
Thunder \Thun"der\, n. [OE. [thorn]under, [thorn]onder,
[thorn]oner, AS. [thorn]unor; akin to [thorn]unian to
stretch, to thunder, D. donder thunder, G. donner, OHG.
donar, Icel. [thorn][=o]rr Thor, L. tonare to thunder,
tonitrus thunder, Gr. to`nos a stretching, straining, Skr.
tan to stretch. [root]52. See Thin, and cf. Astonish,
Detonate, Intone, Thursday, Tone.]
1. The sound which follows a flash of lightning; the report
of a discharge of atmospheric electricity.
2. The discharge of electricity; a thunderbolt. [Obs.]
The revenging gods
'Gainst parricides did all their thunders bend.
3. Any loud noise; as, the thunder of cannon.
4. An alarming or statrling threat or denunciation.
The thunders of the Vatican could no longer strike
into the heart of princes. --Prescott.
Thunder pumper. (Zool.)
(a) The croaker (Haploidontus grunniens).
(b) The American bittern or stake-driver.
Thunder rod, a lightning rod. [R.]
Thunder snake. (Zool.)
(a) The chicken, or milk, snake.
(b) A small reddish ground snake (Carphophis amoena syn.
Celuta amoena) native to the Eastern United States;
-- called also worm snake.
Thunder tube, a fulgurite. See Fulgurite.