A condition one gets when they are so desperate for a boyfriend or girlfriend, that they are beyond merely "thirsty." Their mouth is figuratively as dry as the Mojave Desert.
Bro #1 "Man, that chick is thirsty! That's a turnoff bro!"
Bro#2 "Tell me about it, that chick has straight up Mojave Mouth! I thought I saw a tumble weed fall out!"