1 definition by Gordon feetman

Top Definition

A map on the popular half life 2 mod

garrys mod, it contaons a large field with small mountains in the distance, it also contains an arch like structure in the middle of it containing a secret room.

"Hey wanna go build a spaceship in gm_flatgrass?"

by Gordon feetman January 27, 2021

Buy a gm_flatgrass mug!