What is Undersheriff?

Legal Definition
An undersheriff is an office derived from ancient English custom and remaining in, among other places, England and Wales and the United States, though performing different functions.
-- Wikipedia
Legal Definition
A deputy of a sheriff. The principal is called high-sheriff, and the deputy the under-sheriff. Vide 1 Phil . Ev. Index, h. t.
-- Bouviers Law Dictionary
Legal Definition
An officer who acts directly under the sheriff, and performs all the duties of the sheriff's office, a few only excepted where the personal presence of the high-sheriff is necessary. The sheriff is civilly responsible for the acts or omissions of his under-sheriff. Mozley & Whitley. A distinction is made between this officer and a deputy, the latter being appointed for a special occasion or purpose, while the former discharges, in general, all the duties required by the sheriff's office,
-- Black's Law Dictionary