Pilaster — Chambers's Encyclopaedia

Pilaster, in Classical Architecture, a square pillar, sometimes standing free, but usually attached to a wall, from which it projects $\frac{2}{3}$ th, $\frac{1}{4}$ th, or other definite proportion of its breadth. Greek pilasters, or antæ, were of the same breadth from top to bottom, and had different capitals and bases from those of the orders with which they were associated. The Romans gave them a taper like the columns, and the same capitals and bases.

A detailed black and white illustration of a classical pilaster. It features a square shaft with vertical fluting, a highly ornate capital with acanthus leaves, and a base with a decorative molding. The pilaster is shown attached to a wall, with its top projecting slightly from the wall surface. — Pilaster.