- operating, moving, transferring, flowing, transmitting, receiving, or responding in two directions, usually opposite. There are numerous examples, including bidirectional buses, bi-directional bar code scanners, bidirectional antennas, and bi-directional transistors. Bilateral and bi-directional may be contrasted in the following manner: bilateral refers to the two sides of something, while bi-directional pertains to two directions. Though not necessarily the same, these terms are sometimes used synonymously. Also spelled bidirectional.