Tourelle (architecture)
A tourelle is a type of turret, sometimes used in Chateauesque architecture.
A general dictionary defines tourelle as "a small tower ".
An architectural dictionary defines it more specifically as a "corbelled turret, circular in plan, cone-roofed, sometimes containing a circular stair, set at the angle of a tower or wall at high level, and common in Scottish-Baronial architecture".
A distinction may be made between turrets that are atop corner towers going all the way down to the ground, vs. turrets that project out and up. A tourelle is the latter.