Fluctuate/ˈflʌktʃueɪt/ Definition 1 of 2Pro Tip 1/3Economic Context Often used in economics to describe unpredictable market changes or price variations. Stock market values fluctuate daily. Pro Tip 2/3Weather Changes Used to describe weather patterns that are not stable or predictable. The forecast shows that temperatures will fluctuate this week. Pro Tip 3/3Emotional Variation Can refer to rapid changes in emotions or moods. His mood tends to fluctuate when he's under a lot of stress.