1. A Person who, being unable to express his anger through physical violence (owning to their physical weakness, lack of bravery and/or conviction in real life), instead manifests said emotions through the text-based medium of the internet, usually in the form of aggressive writing that the Keyboard Warrior would not (for reasons previously mentioned) be able to give form to in real life.
2. The term is a combination of the word 'keyboard' (the main tool by which the person expresses his/her latent rage) and 'warrior' (due to the warrior-like aggression, tendency towards violence, headstrong nature and propensity towards brute force as a means of resolving conflict rather than more subtle means dependant on finesse).
3. The Keyboard Warrior seeks to use the power imbued in his 'weapon' to effect death and destruction (in a strictly-metaphorical sense) upon his foes (other virtual identities he has encountered on the internet). In essence, the keyboard (ie. text input ability) allows the keyboard warrior to manifest his true warrior nature in a safe and removed environment, from which no real-life repercussions .
4. Keyboard Warriors are generally identified by unneccessary rage in their written communications, and are regarded as 'losers' by other virtual identities on the internet.

A person who acts tough, or puts down others over the internet.

A warrior who physically wields a keyboard as his main weapon.

some insecure, sad souls who spread bullshit on internet about people on forums like this one

A term coined by vocalist Mandy Lion (WWIII, Wicked Alliance) which is used to describe a "new breed of idiots which use the internet to mudsling people who actually have lives and careers" basically meaning pathetic losers who talk shit about people on the internet for no reason based on nothing e.g. calling someone a failure because they are not hugely successfully or bullying someone for the way they dress etc.

Some one who makes/uses agressive words against some one on the interenet (especially msn and forums. Usally a quiet small natured persopn in real life.

A Keyboard Warrior is someone who deliberately sends inflamatory,rude, agressive or derogatory emails for the purpose of making the recipient of the email get angry or upset.

He/she will also generally Copy as many people as possible on the email, becuase they are under the erroneous impression that they are being witty/funny and that everyone will agree with their comments.

In person they are usually quite timid and do not like direct confrontation. They generally have deep rooted mental issues of depression and or rejection usually becuase they have small dicks and they were breast fed till the age of 10.