The Collaborative International Dictionary of English v.0.48:
Carrier \Car"ri*er\, n. [From Carry.]
1. One who, or that which, carries or conveys; a messenger.
The air which is but . . . a carrier of the sounds.
2. One who is employed, or makes it his business, to carry
goods for others for hire; a porter; a teamster.
The roads are crowded with carriers, laden with rich
3. (Mach.) That which drives or carries; as:
(a) A piece which communicates to an object in a lathe the
motion of the face plate; a lathe dog.
(b) A spool holder or bobbin holder in a braiding machine.
(c) A movable piece in magazine guns which transfers
the cartridge to a position from which it can be
thrust into the barrel.
Carrier pigeon (Zool.), a variety of the domestic pigeon
used to convey letters from a distant point to to its
Carrier shell (Zool.), a univalve shell of the genus
Phorus; -- so called because it fastens bits of stones
and broken shells to its own shell, to such an extent as
almost to conceal it.
Common carrier (Law.) See under Common, a.