A woman's excuse for acting like a bitch, but an insult when accusing them for having it.
During these times where they become Ultra Bitch, they will: consume random things and people, eyes will turn blood red, mouths will foam, talons will grow, show their hatred for man, and wreak havoc for the sake of 'they can' because it is considered an excuse. Women will scream, growl, snarl, bark and possibly devour you whole, and say "sorry I have PMS" afterwards.
CAUTION: Stay away from all women with PMS, if you hear a growl... run. Run as far as you can.
guy: "Hey wassup?"
guy: "Oh God! She's infected!"
girl: *chases boy and eats him whole*
girl: "I'm f*^%ing sorry I have PMS"