A person, typically male, who says or does things that cause you to give them a 'what-are-you-even-doing-here' look. The 'what-are-you-even-doing-here' look is classified by a glare in the tool's direction and is usually accompanied by muttering of how big of a tool they are. The tool is usually someone who is unwelcome but no one has the balls to tell them to get lost. The tool is alwasys making comments that are out-of-place, out-of-line or just plain stupid. The tool is always trying too hard to fit in, and because of this, never will. However, the tool is useful because you can use them for things; money, rides, ect.
"Let's drive to Chicago from Iowa. Oh man, we need money. Hey, let's ask tool to come, he'll spot us the cash!"
"Tool is our friend. We call him that because he is one."