A teenager who emits an aura of obnoxiousness. Also typically picks fights and looses and always talks back to people of authority. Looks like a rodent.
A ratboi is a type of player in Rainbow Six: Siege who will purposely choose recruit and use the M870 as their primary weapon. Ratboi can be used as a noun, and as an adjective.
Usually found in online games, especially cooperative ones. When some little 11 year old faggot thinks it's another episode of some gay anime show or something, and goes out to be a LONE MERCENARY FAGGOT but ends up getting fucked up when he leaves his group, because the sole purpose of the group was to work together to kill monsters that they couldn't normally kill anyway. People like this usually never learn, because ramboism is usually a cause of impatience. The term derives from Rambo, who was the stereotypical lone badass.
SSJ4Gogeta666 suffered from a bad case of Ramboism when his Warrior went off by himself to attack some level 26 monsters in his group that he could never kill anyway because he was level 20.