A collection of mucus, often tinged with blood, that blocks the cervix during pregnancy; known as the "bloody show" when discharged prior to labor. The texture and amount of mucus discharged varies greatly from woman to woman.

I just started my pre-pregnancy reading. I am trying to find out everything I can about this crazy process before I enter it. I had never even heard of the mucus plug until I read about it in Ayun Halliday's The Big Rumpus. I asked my mother-in-law if she remembers losing hers and she didn't even know what one was!

As Ayun writes, "Its appearance means the seal is broken. The cervix is ready for action."

Also spelled "mucous plug".