Cosmic Doom is another way to describe stoner rock, desert rock, Space Rock, riff rock, and fuzz rock.
It is thought to be Pioneered by bands in the 70's such as Black Sabbath, Blue Cheer, Hawkwind, and Captain Beyond.
Many newer bands are also taking this genre to new levels. Make sure to check out all my info on these types of bands.
The main sound behind this type of music it the apparent Psychadelic Vibe you get listening to it. It tends to Swirl and almost lift you from your seat. Many of the bands will add noise in the background of their songs to emphasize this. The sound is always Heavy too and can be a slow riff. Look to my description of doom for more coverage of the tones.