What they are:
A claymore is a two handed Scottish great sword. The origin of the name claymore comes from the Gaelic words ‘claidheamh mòr’ meaning ‘great sword.’
What they look like: Claymores have a long two handed hilt made with a spiral carved wooden handle covering the full tang with a cross guard angled toward the blade. The intention behind this may have been to catch an enemy’s blade behind the crossguard providing an opportunity to kill or disarm him. The crossguard of a claymore traditionally ends with a quatrefoil on each side, and the blade is traditionally between four-and-a-half and five feet long. It includes a blunt section known as a ricasso. This would sometimes be wrapped in leather, enabling the wielder to use it as a leverage point if his opponent managed to come to close grips with him. Thus the sword would be agile enough to allow a contest even at very close quarters in spite of the blade’s great size and weight.
This is a stainless steel replica of a claymore from Scotland. In all respects except materials, it closely resembles a historic piece which survived. Image is courtesy of http://www.sears.com/irc-claymore-sword-52inch-overall-red-handle/p-SPM7317624313?prdNo=1&blockNo=1&blockType=G1
How they were used: these great swords were used for close quarters combat but also gave some reach to the swordsman potentially allowing him to strike at his adversary before he himself was at risk of counter attack.
Scottish highlanders likely used claymores against the british and in border wars with other Scottish tribes as a weapon of intimidation because of the weight of the weapon and length of the blade. This presented some difficulty when fighting in close ranks because the weapon seemed to be less about control and more about intimidation.
History of the claymore: the first claymores likely appeared in the late 1300s and were used up until the 1700s.
They were likely used by William Wallace and his men, however Wallace seems to have carried a custom sword that does not fit the exact qualifications of a claymore. Despite this, it is likely that both claymores and highlanders were brought fame because of the campaigns fought by the Scottish against British oppression following the lead of William Wallace.