警报 (jǐng bào) literally combines 警 (jǐng), meaning 'to warn' or 'alert', and 报 (bào), meaning 'to report' or 'to announce'. Together, they form a noun meaning 'alarm'—specifically a loud, attention-grabbing sound signaling danger, malfunction, or urgent need for action. It is commonly used in contexts like fire alarms, security systems, medical monitors, and weather warnings.

Unlike the more general word 报警 (bào jǐng, 'to call the police'), 警报 refers only to the audible (or sometimes visual) signal itself—not the act of reporting. It often appears with classifiers like 一个 (yī gè) or in compound terms such as 火警报警器 (huǒjǐng bàojǐngqì, 'fire alarm device') or 空袭警报 (kōngxí jǐngbào, 'air raid siren'). The tone on both characters is third tone, and care should be taken not to mispronounce 报 as fourth tone (bào is correct; bāo or bào without tone mark is incorrect).