Definitions:

1. A motion like that of waves; a moving in this and that direction. NOUN
   • The scientist recorded the fluctuation in water levels over several months.
2. A state of being unstable, varying, or prone to change. NOUN
   • The fluctuation in temperature made it hard to plan outdoor activities.
3. The act or precess of changing or varying, often within a range. NOUN
   • There was a significant fluctuation in the stock market prices today.

Synonyms:

• Instability
• oscillation
• shift
• swing
• Variation
• volatility