Initialism of over-the-horizon backscatter (“a form of radar”).

(inorganic chemistry) Any salt of phosphoric acid in which only one of the hydrogen atom has been replaced by a metal ion. / (organic chemistry) Synonym of diphosphate.

(of a body of water) Traversable by raft.

A diminutive of the male given name Robert. / A diminutive of the female given name Roberta.