over and under

noun3

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.
3. •
   (slang) Synonym of speedball (“type of illicit drug”).