From The Collaborative International Dictionary of English v.0.48:
Jointer \Joint"er\, n.
1. One who, or that which, joints.
[1913 Webster]
2. A plane for smoothing the surfaces of pieces which are to
be accurately joined; especially:
(a) The longest plane used by a joiner.
(b) (Coopering) A long stationary plane, for planing the
edges of barrel staves.
[1913 Webster]
3. (Masonry)
(a) A bent piece of iron inserted to strengthen the joints
of a wall.
(b) A tool for pointing the joints in brickwork.
[1913 Webster]