Webster’s 1913 has no entry under this spelling.
Shades of meaning
Fernald has no entry of its own for rub off; he lists it under cancel.
Where he writes about it:
To cancel is, literally, to make a lattice by cross-lines, exactly our English cross out; to efface is to rub off, smooth away the face, as of an inscription; to erase is to scratch out, commonly for the purpose of writing something else in the same space; to expunge, is to punch out with some sharp instrument, so as to show that the words are no longer part of the writing; to obliterate is to cover over or remove, as a letter, as was done by reversing the Roman stylus, and rubbing out with the rounded end what had been written with the point on the waxen tablet. — from cancel