A thunderbolt is a dramatic flash of lightning, especially one that seems to strike the earth with tremendous force. When you see a brilliant streak of electricity tear through a dark storm cloud and hear the explosive crack of thunder that follows, you're witnessing a thunderbolt. The word captures the violent, sudden power of a lightning strike: bolt suggests something thrown or shot (like an arrow or bolt from a crossbow), while thunder is the booming sound that lightning creates.

In ancient times, people thought gods like Zeus or Thor literally hurled thunderbolts as weapons. We now know lightning is a massive electrical discharge, but the word still carries that sense of awesome, destructive power. A thunderbolt can split trees, start fires, or blast holes in the ground.

The word also describes anything that arrives with shocking suddenness. If your teacher announces a surprise test, you might say it hit you like a thunderbolt. When someone receives startling news out of the blue (another weather phrase!), you might say it came like a thunderbolt. The famous phrase “a bolt from the blue” means something completely unexpected, referring to lightning that seems to flash from a clear blue sky.