pithole
Pithole as the name suggests they are unavoidable bumps in the road of life, usually the nastiest, ugliest least attractive woman you will even encounter. When driving down the road of life you try to avoid pitholes whenever possible, but its inevitable that every once in a while you will hit a pithole.
When walking in the mall, your friend sees a horribly ugly woman, he says "watch out for that pithole" to get your attention. Due to his quick thinking, you both avoid this troll.