The basic meaning of this word—composed of the preposition b ('in,' 'upon') and the noun 'eber ('ford,' 'a place for passing over')—is 'on the other side of' or 'beyond' whatever is the point of reference.
Though frequently translated as "east of" in NIV, the word is, of itself, directionless. In the book of Joshua, e.g., it is rendered "east of [the Jordan]" in 1:14 & 15 but "west of [the Jordan]" in 5:1. Most other translations leave the word as "on the other side of [the Jordan]" leaving the reader to decipher from the context which side is referred to.