(noun) This is a sex toy used by lesbians in pairs to enjoy a cock without having to deal with men.
What makes this sex toy popular is the fact that both women bask in the orgasm of each other. The more one tries, the better it feels for her and her partner. It's kinda mutual.
Other versions of this toy include squirters at each of the heads and vibrators
Lesbian 1: I miss cock.
Lesbian 2: I'm horny and I too miss cock and I hate men.
Lesbian 1 & 2 (together): LET'S USE A DOUBLE DONG!
(15 minutes later): *sighs of relief and orgasm