Claymore may refer to one of six things, as far as I am aware of.

Most commonly, it is used about a two-handed scottish sword, famously carried by William Wallace in Braveheart, or the anti-personnel mine named after that weapon, the M18A1 Claymore. It is, however, confusingly also used about another kind of scottish sword, a broadsword, as well as (less confusingly) the name of a suburb of Sydney, a defunct American football team, and a manga. This writeup focuses on the swords.

The two-handed scottish claymore was used from around 1500 until maybe 1700 (so the use of the weapon in Braveheart seems to be anachronistic), and was somewhat shorter than the Zweihander of the german Landsknechts, with a typical blade length of 105-110 cm, and a hilt of 30ish cm. It seems it usually weighted in at about 2.5kg.

The basket-hilted claymore is an entirely different sword, more similar to the spanish schiavona. It is a straight, double-egded and single-handed weapon with a blade length of maybe 80-85cm (this length comes indirectly, from replica weapons I've seen), sporting a basket hilt that protects the hand of the wielder, and was in use from around 1700 until, I would suppose, WWI. It even saw some use in WWII, where English Commando Officer "Fighting" Jack Churchill successfully used it several times. Officers of the Royal Regiment of Scotland still carry these claymores as part of their ceremonial dress.

While some claim that the basket-hilted claymore is wrongly named, it is named so from historical sources. In fact, it seems that the first known written instance of the word "claymore" comes from after the two-handed sword was out of use, and replaced by the basked-hilted weapon.