Jointer n. : One who, or that which, joints.

Jointer n. : A plane for smoothing the surfaces of pieces which are to be accurately joined

Jointer n. : The longest plane used by a joiner.

Jointer n. : A long stationary plane, for plaining the edges of barrel staves.

Jointer n. : A bent piece of iron inserted to strengthen the joints of a wall.

Jointer n. : A tool for pointing the joints in brickwork.

Example:
I have a crescent 12 inch Jointer what is one worth?

Taxonomy
jointer, cutter head, timber, jointer plane, infeed, knives, outfeed table, work piece, boards, thickness planer, free encyclopedia, edge, perpendicular, Australia, flat surface, moveable fence, blade, Articles lacking sources.

Defination from the web:
jointer derives its name from its primary function of producing flat edges on boards prior to joining them edge-to-edge to produce wider boards. ... Fundamentally, a jointer consists of two parallel tables, a moveable fence which is normally set perpendicular to the tables, and a cutter head ...