over and under

Noun

 * 1) A double-barreled shotgun (or infrequently a rifle), with one barrel placed on top of the other.
 * 2) An obstacle in obstacle-course racing composed of multiple bars, with bars set at various heights, where the competitor must pass over high bars and pass under low bars.
 * 1) An obstacle in obstacle-course racing composed of multiple bars, with bars set at various heights, where the competitor must pass over high bars and pass under low bars.