It refers to male citizens with no special rank or title, that is, seitei (adult man) and rotei (old man at the age of 61 to 65, later changed to 60 to 64 under ritsuryo system) who rendered yo (tax in kind in lieu of labor) and cho (tax on product).
無位無官の公民、すなわち庸と調を負担した正丁・老丁男子を指す。