One of the three orders or organisational systems of Ancient Greek or classical architecture characterised by columns which stood on the flat pavement of a temple with a base, their vertical shafts fluted with parallel concave grooves topped by a capital decorated with acanthus leaves, that flared from the column to meet an abacus with concave sides at the intersection with the horizontal beam that they carried.

Source: https://en.wikipedia.org/wiki/Glossary_of_architecture