Easton's Bible Dictionary
Frequently referred to by the sacred writers (Nahum 1:3-6). Thunder and lightning are spoken of as tokens of God's wrath (2 Samuel 22:15; Job 28:26; 37:4; Psalm 135:7; 144:6; Zechariah 9:14). They represent God's glorious and awful majesty (Revelation 4:5), or some judgment of God on the world (20:9).
Noah Webster's New International Dictionary of the English Language
1. (n.) A discharge of atmospheric electricity, accompanied by a vivid flash of light, commonly from one cloud to another, sometimes from a cloud to the earth. The sound produced by the electricity in passing rapidly through the atmosphere constitutes thunder.
2. (n.) The act of making bright, or the state of being made bright; enlightenment; brightening, as of the mental powers.
3. (vb. n.) Lightening.