Unsettle, v. t.
Etymology: [1st pref. un- + settle.]
To move or loosen from a settled position or state; to unfix; to displace; to disorder; to confuse.
1 other Webster entry under this spelling
Unsettle, v. i.
To become unsettled or unfixed; to be disordered. Shak.
Shades of meaning
Fernald has no entry of its own for unsettle; he lists it under displace.
He lists it without comment; the entries above explain its neighbors.