A biological robot. The term is rarely defined any further, but I believe that in Rendezvous With Rama it was specified that while they were largely composed of biological tissue, they did not have the organs necessary to digest food. Biots may also had some metal parts (cybiot?). To the best of my knowledge, biots exist only in science fiction worlds.
Compare to robot, android, cyborg, and clone.
BIOT stands for British Indian Ocean Territory