headlight

noun

1. A bright light, with a lens and reflector, on the front of a motor vehicle (or originally a ship or train), designed to illuminate the road when driving at night; normally one of a pair.

   “Improving how headlights are designed and controlled does not have to mean choosing between environmental protection and public safety. Smarter lighting that reduces unnecessary brightness and glare can benefit wildlife, improve driver comfort, and support safer nighttime travel.”

2. (US, in-plural, slang, vulgar)A woman's breast.

   “Oh, well. She's got... great... casabas.[…]Well, you know. Melons.[…]Hoo-has? Honkers? Hooters? Headlights? Uh... tatas? Teeters? Tweeters? Tom-toms? Tetons?[…]I'm trying to say it. Uh, meatballs. Mangoes. Cream pies. Cupcakes? Uh... bangers? Bouncers? Bulumbas?[…]Bazongas? Breasts! I said it.”

3. (Canada, in-plural, slang, vulgar)A woman's erect nipples, partially masked by clothing.
4. (US, in-plural, slang)A jewel; especially a diamond.
5. (US, in-plural, slang)Lysergic acid diethylamide (LSD).