挫 is a formal verb meaning 'to defeat, frustrate, or dampen'. It is most often used in compound words like 挫败 ('to thwart'), 挫折 ('setback'), and 挫伤 ('to dampen morale'). The sense 'deflate' captures how it can refer to deflating someone's enthusiasm or confidence. As a single character verb, it tends to appear in written or literary contexts rather than casual speech.