From The Collaborative International Dictionary of English v.0.48 :
Planer \Plan"er\, n.
1. One who, or that which, planes; a planing machine; esp., a
machine for planing wood or metals.
[1913 Webster]
2. (Print.) A wooden block used for forcing down the type in
a form, and making the surface even. --Hansard.
[1913 Webster]
Planer centers. See under Center.
[1913 Webster]
From WordNet (r) 3.0 (2006) :
planer
n 1: a power tool for smoothing or shaping wood [syn: plane,
planer, planing machine]