2: An expression used when a person "invents", unknowingly, an already existing sexual novelty.
Bob: Dude, me and Linda totally did a double decker last night!
Frank: Bro, it's called 69. No need to reinvent the dildo.
Bob: I came up with this awesome idea last night. Just hear me out, but what if we video tape people doing it and put it on the internet??
Frank: Bob, it's called porn. Stop reinventing the dildo.