Definitions
1.adjectiveOf a surface: flat or level.
2.nounA woodworking tool which smooths a surface or makes one surface of a workpiece parallel to the tool's bed.
3.nounA large machine tool in which the workpiece is traversed linearly (by means of a reciprocating bed) beneath a single-point cutting tool. (Analogous to a shaper but larger and with the workpiece moving instead of the tool.) Planers can generate various shapes, but were most especially used to generate large, accurate flat surfaces. The planer is nowadays obsolescent, having been mostly superseded by large milling machines.
4.nounA wooden block used for forcing down the type in a form, and making the surface even.