A vector trap a mechanism found in Orbital Frames that compresses space in a certain radius around the Orbital Frame. The range of the Vector Trap itself varies with Orbital Frames.
The orbital frames Anubis and Hathor are able to use their vector traps for an effect described as the same as a Urenbeck Catapult to essentially teleport themselves while Jehuty and Dolores make use of this mechanism to store weapons and other items.
A Vector Trap creates a sort of "hammerspace" and is used to explain how Jehuty is able to carry its sub-weapons. In the anime, Dolores makes use of it to store various mines as well as its own version of Jehuty's familiar weapons, such as the Halberd.