The loud sound that follows a flash of lightning. It is due to the sudden expansion of air that has been heated by such electrical discharge, causing the air to move violently away from the lightning’s path and then back again behind it.​—Job 28:26; 38:25.

The Hebrew verb ra·ʽamʹ (meaning “thunder”) is at times mentioned in connection with Jehovah (1Sa 2:10; 2Sa 22:14; Ps 18:13), the One who has on occasion employed thunder to accomplish his will. For example, in the time of Samuel, Jehovah threw the Philistines into confusion by means of thunder (Heb., raʹʽam). (1Sa 7:10; compare Isa 29:6.) Another Hebrew word, qohl, sometimes translated “thunder” (1Sa 12:17, 18, ftn), basically means “sound” (Ex 32:18, 19) or “voice.”​—De 21:18; 1Ki 19:12.

The awesome sound of thunder is associated with Jehovah’s voice. (Job 37:4, 5; 40:9; Ps 29:3-9) When certain Jews heard Jehovah speak from heaven to Jesus, there was a difference of opinion whether the sound was thunder or the voice of an  angel. (Joh 12:28, 29; compare Re 6:1; 14:2; 19:6.) The sound of thunder often being an advance indication of an approaching storm, “thunders” can designate divine warnings, as at Revelation 8:5; 10:3, 4; 16:18.

To the Jews at the foot of Mount Sinai, the thunder that they heard was a manifestation of God’s presence. (Ex 19:16; compare Re 4:5; 11:19.) Either this event or God’s leading Israel by means of a pillar of cloud (a place of thunder) may be alluded to by the psalmist’s words: “I [Jehovah] began to answer you in the concealed place of thunder.”​—Ps 81:7.