We don't have synonyms for nanobot yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are nanodot.
(n) :
(nanotechnology, robotics) A very small autonomous robot, typically the size of a biological cell, designed to work alone or in very large numbers to achieve some task.
(n) :
(nanotechnology, robotics) A very small autonomous robot, typically the size of a biological cell, designed to work alone or in very large numbers to achieve some task.