A firearm, usually a handgun or revolver, which is kept and intended to be fired once or only during one incident, usually for illegal purposes, and then discarded so as to remove suspicion from the weapon's user. Serial numbers may be filed off and the gun is usually unregistered and illegal to even own, and care is always taken to not leave prints on the gun so that it can't be traced back to the owner that way should it ever be discovered. Usually kept somewhere hidden and safe as a "Plan B" should the owner ever need to have access to a gun that can't be traced back to them.
Person A: dude, what are you going to do with that?
Person B: I just discovered my wife was cheating on me with my boss. I need this throw away gun I have so I can kill them for it. That way no one can trace the gun back to me and there won't be any witnesses.
Person A: but, dude, I'm a wit...oh sh-
Person B: *KABLAM*
In online gaming, a throw away account is an account made with no intentions of playing the game long-term on that specific account.
Often, people create throw away accounts for malicious purposes, such as spamming or cheating in-game.
The accounts often get banned for breaking rules. People use throw away accounts to prevent their mains from getting banned.
Throw away accounts are often used for people who use macros, or computer software to play the game for them and to gain an unfair advantage. This is almost always against the rules of the game and will result in banning. The hope is that the throw away accounts do not get banned, and acquired wealth can be transfered to another account.