Co·lum·nar a.  Formed in columns; having the form of a column or columns; like the shaft of a column.
 Columnar epithelium Anat., epithelium in which the cells are prismatic in form, and set upright on the surface they cover.
 Columnar structure Geol., a structure consisting of more or less regular columns, usually six-sided, but sometimes with eight or more sides. The columns are often fractured transversely, with a cup joint, showing a concave surface above. This structure is characteristic of certain igneous rocks, as basalt, and is due to contraction in cooling.

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