Acronym for Designated Cock Blocker. This is the most unattractive female in a group of women at a nightclub or like social gathering. Her primary purpose is to remain unintoxicated and defer all advances from would be suiters.
Also, the male counterpart is the friend who won't go home or go away when you are trying to get your freak on, as it were.
O.k., first and foremost, we have to distract the D.C.B., so we can make our move.