A person convinced by his/her peers and by society that they must act a certain way to be accepted. This typically consists of blaming other people for your problems, never getting over high school, wearing your pants halfway down your legs, and believing your kindergarten teachers when they said you were special.
Studies show that 95% of tools are unaware of the word's actual meaning, and will misuse it on a regular basis.
American tools have overused the word so much that, along with gay, retarded, and a deer having been killed on major state highway, it has transformed into something completely different, and now simply means, "that guy I don't like."