A member of the Parliamentarian party in the English civil war -- so called from his habit of wearing his hair short, whereas his enemy, the Cavalier, wore his long. There were other points of difference between them, but the fashion in hair was the fundamental cause of quarrel. The Cavaliers were royalists because the king, an indolent fellow, found it more convenient to let his hair grow than to wash his neck. This the Roundheads, who were mostly barbers and soap-boilers, deemed an injury to trade, and the royal neck was therefore the object of their particular indignation. Descendants of the belligerents now wear their hair all alike, but the fires of animosity enkindled in that ancient strife smoulder to this day beneath the snows of British civility.

A nickname for a Puritan. See Roundheads, the, in the Dictionary of Noted Names in Fiction.

a supporter of Parliament and Oliver Cromwell during the English Civil War

The Roundheads was the nickname given to the supporters of Parliament during the English Civil War. They were called this because they called the supporters of Charles I cavaliers and in return the cavaliers gave roundheads a nickname because they wore closely cropped hair that was uncommon at that time.

A roundhead was a type of mace used during the English Civil War. It is described as having a head about nine inches long, a staff two yards long inserted into the head, twelve iron spikes round about, with another spike in the end. This was a very useful weapon, because the mace could penetrate most armor easily.