from
The Collaborative International Dictionary of English v.0.48
Columnar \Co*lum"nar\, a. [L. columnaris, fr. columna.]
Formed in columns; having the form of a column or columns;
like the shaft of a column.
[1913 Webster]
{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.
[1913 Webster]