A Bomb Space Jump (also called the BSJ) is a sequence-breaking technique in Metroid Prime, Metroid Prime 2: Echoes, and Metroid Prime 3: Corruption. First, the player must put Samus's back to the wall, Morph Ball, then change the camera angle so the wall she put her back up against is no longer visible, jump using the Bomb Jump or Spring Ball, unmorph in midair and Space Jump. It is also possible to use the Screw Attack after the jumps to gain access to Hidden Worlds or to Sequence Break.
There is another variant of this trick known as a 3-BSJ (Triple Bomb Space Jump). It uses a triple or double bomb jump to gain more height with the jump, but is otherwise the same.
These techniques were removed in the Metroid Prime Trilogy re-release.
In Metroid and Metroid II: Return of Samus, this technique can also be used via a Double Bomb Jump in conjunction with the Midair Jump Glitch. Using the technique allows access to various areas without the use of the High Jump Boots or Ice Beam, but the technique is made more versatile if Samus does have the High Jump Boots (and, in Metroid II, the Spring Ball).
Pages from Metroid2002.com on how to do a Bomb Space Jump: