Definition of pillar

• n. - The general and popular term for a firm, upright, insulated support for a superstructure; a pier, column, or post; also, a column or shaft not supporting a superstructure, as one erected for a monument or an ornament.
• n. - Figuratively, that which resembles such a pillar in appearance, character, or office; a supporter or mainstay; as, the Pillars of Hercules; a pillar of the state.
• n. - A portable ornamental column, formerly carried before a cardinal, as emblematic of his support to the church.
• n. - The center of the volta, ring, or manege ground, around which a horse turns.
• a. - Having a support in the form of a pillar, instead of legs; as, a pillar drill.