What is Habere Facias Possessionem?

Legal Definition
Practice, remedies. The name of a writ of execution in the action of ejectment.

2. The sheriff, is commanded by this writ that, without delay, he cause the plaintiff to have possession of the land in dispute which is therein described; a fi. fa. or ca. sa. for costs may be included in the writ. The duty of the sheriff in the execution and return of that part of the writ, is the same as on a common fi. fa. or ca. sa. The sheriff is to execute this writ by delivering a full and, actual possession of the premises to the plaintiff. For this purpose he may break an outer or inner door of the house, and, should he be violently opposed, he may raise the posse comitatus. Wats. on Sher. 60, 215; 5 Co. 91 b.; 1 Leon. 145; 3 Bouv. Inst. n. 3375.

3. The name of this writ is abbreviated hab. fa. poss. Vide 10 Vin. Ab.14; Tidd's Pr. 1081, 8th Engl. edit.; 2 Arch. Pr. 58; 3 Bl. Com. 412; Bing. on Execut. 115, 252; Bac. Ab. h. t.
-- Bouviers Law Dictionary
Legal Definition
Lat. That you cause to have possession. The name of the process commonly resorted to by the successfui party in an action of ejectment, for the purpose of being placed by the sheriff in the actual possession of the land recovered. It is commonly termed simply "habere faeias," or "hab. fa."
-- Black's Law Dictionary
Legal Definition
A writ to enforce a plaintiff’s judgment in ejectment and put him in possession.
-- Ballentine's Law Dictionary