'Dǎ léi' literally means 'to hit thunder' — a vivid, idiomatic expression describing the natural phenomenon of thunder occurring during a storm. While 打 (dǎ) usually means 'to hit' or 'to strike', and 雷 (léi) means 'thunder' or 'lightning', together they form an inseparable verb meaning 'to thunder'. It does not refer to lightning itself (which is 闪电, shǎn diàn), but specifically to the loud, rumbling sound produced by atmospheric electrical discharge. This word is commonly used in weather reports, storytelling, and everyday descriptions of storms.

The phrase always functions as a verb and is typically used in the present or past tense with aspect particles like 了 (le) or 正在 (zhèngzài). It rarely appears alone — it's most natural when paired with related weather terms like 下雨 (xià yǔ, 'to rain') or 刮风 (guā fēng, 'to blow wind'). Unlike English 'thunder', which can be both noun and verb, 打雷 is almost exclusively verbal in modern usage and never used as a standalone noun (e.g., you wouldn’t say *这个打雷很响*; instead, say *这雷打得很响*).