What is blackroom in gay sex?

A special room, painted in a flat black color, from floor to ceiling, that is used in Sadomasochism sexual play.

Definition

While traditional 'blackrooms' are meant for heavy SM play, they are no different than any other 'dungeon' used in BDSM play.

These 'rooms' generally are of varying colors, mostly dark, in order to set a mood, or accentuate the sex play.  Various BDSM toys such as chains, slings, and other specialized apparatuses, are located in these sex playrooms.