1- An invention that's meant to make things easier, but doesn't work or even makes things worse instead of better.
2- When someone invents something that's already been invented.
Dude#1 - My new MAC is supposed to have voice recognition to let me log in, but it's a total piece of crap and it never works.
Dude#2 - Yeah man ... Logging in with a keyboard is much faster and easier. Voice recognition is a total unvention.
Dude#1 - Did you check out that Volvo demonstration with automatic brakes that are supposed to stop you from having a collision? It crashed in front of everyone!
Dude#2 - Yeah, that's a total unvention.