From Webster's Third New International Dictionary:
DOFF (noun) = the act of removing material from a textile-manufacturing machine; also: material so removed.
DOFF (verb) = to remove (material) from a textile-manufacturing machine <~full bobbins from a spinning frame><~cotton from a carding frame>
DOFFER (noun) =
1a: a small roller usu. covered with wire teeth used to strip material from another roller or cylinder on textile machinery; esp.: a roller on a carding machine
1b: a machine or device for doffing bobbins
1c: a device for stripping cotton from the spindle of a mechanical cotton picker
2: a textile worker who removes full bobbins or cones from machines and puts in empty ones
From these definitions and the fact that your ancestor was located in Georgia, I would guess that he or she was working for a cotton mill or cotton-picking operation.
Check the occupations of the other residents enumerated on the census pages surrounding your ancestor; they may give you more clues.