To unsettle is to make someone feel disconcerted and disturbed. After you watch a scary horror movie, every little sound in your dark house will probably unsettle you.
Things that leave you uneasy or anxious unsettle you, whether you receive a creepy prank phone call or have to start at a new school after moving in the middle of the year. A spooky mystery novel might unsettle you, especially if you read it at night, while falling stock prices tend to unsettle Wall Street experts. Use this verb whenever things feel upsetting and unstable.