Out of Bounds

Out of Bounds (abbreviated OoB) is a rule applied to Super Metroid categories, typically preventing the use of Out of Bounds (e.g. no OoB) in a run.

Out of Bounds is defined as whenever Samus' hitbox leaves the regular boundaries of the room (via X-Ray Climb, Doorskip, or any other glitch) and causes the map to shift into a black area that is not marked in the game and is not tracked. The map on the HUD consequently stops blinking when this occurs (which it does not when Samus is located at black inbounds map square tiles such as the easiest to reach black map square tile in the Green Brinstar Fireflea Room). In Out of Bounds Samus completely leaves the existing room and is able to exploit junk data left behind from previous rooms.

This does not cover clipping through walls and platforms, as well as an X-Ray Climb that goes through the wall but doesn't leave the room (such as leaving Draygon without Gravity).

Kejardon's explanation of out of room travel

Samus is at any point in time during game-play (i.e. outside of where ever the game puts Samus during Intro or Title Screen menuing phases) only allowed to exit the inbounds rectangles of rooms with parts of her bodybox (or her whole bodybox) during standard/default elevator rides (i.e. non-loose ones activated by triggering the yellow elevator platform enemy that continually teleports Samus onto it while it keeps moving, whereas a loose elevator ride can be triggered using Reserves, for example), and while a transitioning process is already going on (since in some cases of entering normal doors normally, the game shifts Samus' bodybox through and past the transition tiles).

For more information also see this post http://tasvideos.org/forum/viewtopic.php?p=433442&highlight=#433442 and the bottom part of this post: http://tasvideos.org/forum/viewtopic.php?p=418314&highlight=#418314