Reg. Z and Reg. C (off the top of my head, there may be others) has a definition of dwelling, and while they're similar, they aren't exact copies of each other. Always a bit dangerous (IMHO) to try to give a sweeping definition of any term that covers the entire compliance world because once you do, you're in danger of the "but you said a dwelling was XYZ". I try to keep all definitions in their own small world (the applicable regulation).
Reg. Z definition: (19) Dwelling means a residential structure that contains one to four units, whether or not that structure is attached to real property. The term includes an individual condominium unit, cooperative unit, mobile home, and trailer, if it is used as a residence.
Reg. C definition: (f) Dwelling means a residential structure, whether or not attached to real property. The term includes but is not limited to a detached home, an individual condominium or cooperative unit, a manufactured home or other factory-built home, or a multifamily residential structure or community.
I'm fixin' to fix that.