GLM (Ghoul Mesh, Ghoul 2 Model File) is a 3D mesh model file format used by the Ghoul 2 game engine from Raven Software, used in such games as Star Wars Jedi Knight: Jedi Academy. It is compiled from the dotXSI format. GLA animation files use this data.
(Searching for "Ghoul Mesh" gets you things like "Bad Ghoul Mesh Socks" that are "BAD GHOUL. She's scary spice gone to hell and back".)