To make upset or uncomfortable
Don't unsettle the horses or they'll bolt.
To bring into disorder or disarray
Disturbed, upset.
I was unsettled by the sudden outburst, and since I didn't know what to do I just stood there, confused.
Not in a steady condition, uncertain, subject to change.
Not populated, having no settlers or other inhabitants.
Unpaid.
We need to settle this bill; even if you think the charge is too high we can't just leave it unsettled.