Mo. Rev. Stat. § 534.020
If any person shall enter upon or into any lands, tenements or other possessions, with force or strong hand, or with weapons, or by breaking open the doors or windows or other parts of a house, whether any person be in it or not, or by threatening to kill, maim or beat the party in possession, or by such words or actions as have a natural tendency to excite fear or apprehension of danger, or by putting out of doors or carrying away the goods of the party in possession, or by entering peaceably and then turning out by force, or frightening, by threats or other circumstances of terror, the party out of possession, and detain and hold the same in every such case, the person so offending shall be deemed guilty of a "forcible entry and detainer" within the meaning of this chapter.
§ 534.020, RSMo