Lean-to — Defs

01 a. Having only one slope or pitch; -- said of a roof.

1.
Having only one slope or pitch; -- said of a roof.(Arch.)

02 n. 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.

1.
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.(Arch.) Also: penthouse, to-fall
“The outer circuit was covered as a lean-to, all round this inner apartment.” — De Foe.
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.