Webster's Revised Unabridged Dictionary · 1913

A document which is a facsimile of another document, converted into electrical symbols by a facsimile machine at one telephone terminal, transmitted via telephone and printed on some form of paper at a facsimile machine at a second telephone terminal. A document transmitted using a computer at one or both ends may also be called a fax if the transmission protocol is similar to that used by telefax devices, that is if the originating or receiving device could be a telefax device.

To transmit a copy of a document (a fax) over a telephone line using facsimile devices or the telefax protocol at both ends. See fax, n., and facsimile{2}, n.