Lean-to
Lean-to , adjective
(Architecture) Having only one slope or pitch; -- said of a roof.
Lean-to , noun
1.
(Architecture) A shed or slight building placed against the wall of a larger structure and having a single-pitched roof; -- called also penthouse, and to-fall.
The outer circuit was covered as a lean-to, all round this inner apartment.
2.
A crude, usually temporary shelter comprising a lean-to roof braced against any convenient support, as a wall, a tree or a pole. The roof may extend all the way to the ground.