‘伺隙’ is a literary, slightly formal verb meaning 'to watch for (and exploit) a weakness, opening, or moment of vulnerability.' The first character 伺 (sì) means 'to wait for' or 'to watch closely,' often with intent; the second character 隙 (xì) means 'crack,' 'gap,' or 'opportunity'—literally a physical or metaphorical opening. Together, they form an idiom-like compound emphasizing patient, strategic observation before action.

This term appears frequently in classical and modern Chinese texts describing animal behavior (e.g., predators stalking prey), military strategy, or competitive human situations like business or debate. It carries a connotation of stealth, timing, and opportunism—not mere chance, but deliberate vigilance. While not used in casual speech, it’s common in written narratives, news analysis, and idiomatic expressions such as 伺隙而动 ('watch for an opening and then act').