Referring to the dimensions of anything (object, event, location), extra-dimensional describes something which exists in more than the three commonly perceived dimensions of length, width, and height (in a cartesion coordinate system, the X, Y, and Z axes).

Commonly time or duration is associated with a fourth dimension, but geometers typically do not, instead recognizing only spatial dimensions. For more on four-d objects, consider a hypercube, AKA tesseract, one of the simplest 4D objects.