Basic Fantasy RPG says:
Fighters include soldiers, guardsmen, barbarian warriors, and anyone else for whom fighting is a way of life. They train in combat, and they generally approach problems head on, weapon drawn.
Not surprisingly, Fighters are best at fighting of all the classes. They are also the hardiest, able to take more punishment than any other class. Although they are not skilled in the ways of magic, Fighters can nonetheless use many magic items, including but not limited to magical weapons and armor.
Well, that's pretty clear. I particularly like the second paragraph which gives me an idea of how the standard template should be like in comparison with the other character classes.
Labyrinth Lord says:
Fighters, as their name implies, are exclusively trained in the arts of combat and war. They are specialists at dealing physical blows. Unlike other classes, fighters are particularly burdened in a group of adventurers because they are tougher and must take the lead to defend others. Fighters can use any weapons and armor.
Shorter than Basic Fantasy RPG, and talks about familiarities with all weapons and armor, and makes a distinction about the ability to 'deal physical blows'. Also there's an emphasis on the role of fighters in a party as defenders due to their toughness. However, there's a suggestion of professionalism here as well, with a word choice of 'exclusively trained' which differentiates them from talented fighters or dangerous barbarians.
Swords & Wizardry says:
Fighters are warriors, trained in battle and in the use of armor and weapons. Perhaps you are a ferocious Viking raider, a roaming samurai, a dashing swashbuckler, a deadly swordswoman, or a chivalrous knight. Whatever type of Fighter you choose to play, you will probably end up on the front lines of your adventuring party—going toe-to-toe with dragons, goblins, and evil cultists, hacking your way through them and taking the brunt of their attacks. The Fighter character is best-equipped of all the character classes to dish out damage and absorb it, too. Clerics heal and Magic-Users cast spells, but the swordplay and archery are generally up to you. You are going to serve as the party’s sword and shield, protecting the weaker party members and taking down the enemies before you.
Verbose in description, it also gives various cultural incarnation of the fighter class. Like LL it talks about the fighter's role in the party, and identifies the strengths of the class in comparison to other character classes.
Fighters are trained in the use of weapons and armour, usually beginning their adventuring careers after a stint of training as a town guardsman, soldier, man-at-arms, bandit, pirate, or mercenary.
Fighters are the backbone of an adventuring party; without them to hold the line, the other members of the party will be overrun before they can bring their own skills to bear. Fighters are the most powerful characters in melee or missile combat, whether on offence or defence. Together with the ranger and paladin, they have the most hit points, and their ability to survive the most brutal battles is therefore unrivalled.
They also have the best chance “to hit” of all the classes, particularly at higher level. They may use any kind of armour, shield, or weapon.
I rather like how it was written. It gave the breadth of roles covered by the character class, identified the role played by the character class in parties, and identifies the combat strengths of the character class when compared to the others.
Consolidated Character Class Guidelines:
Not suprisingly, a Fighter is consistently defined as someone capable of fighting well -- skilled with all weapons and armor, tough in a fight, and so on. Although, in terms of progression, the Underdark Gazette has an interesting view on fighter level progression.
It's not always clear whether the combat ability is purely due to training, or perhaps due to natural skill or talent or curse -- the descriptions differ slightly here. What does matter is that in face-to-face melee combat, the fighter is head and shoulder above all other classes.