Q for Quiet Release Mode
I ll be truthful about it, I couldnt find any other describable photography related word with Q, so here goes. Quiet Release Mode is a shooting mode, available in Nikon DSLR bodies, not sure about the others though, which significantly reduces the sound of the shutter slap. It may be used in sensitive environments, such as in a museum, or when taking a close up of a sleeping beast maybe. It acts similar to the single shot mode, but is a bit slower too. In my camera, its the least used mode.