info_groupspawn is an advanced form of info_mulitspawn. It differs by spawning multiple enemies at once, in a grid pattern. Please read the info_multispawn entry for the basics of how to create a multiple spawner entity, then read below for how to configure the grid.
The wait key is not used. Instead, the monsters are spawned in a grid, spaced “lip” units apart, in rows “t_width” units wide in total. The rows start from the origin of the entity and go north. When the row is full the next row begins to the west of the last one.For example: to get a 3×2 block of monsters 64 units apart, set “lip” to “64” and t_width to “192” You may have to experiment a little to get the placement and values correct. (thanks to Kinn for this idea).