headlight

noun[in the plural]5

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.

   • The indefinite object was drawing away from us at a high speed and eventually disappeared into a veil of atmospherics, very much as a headlight disappearing into a fog. — 1965
2. •
   (slang, vulgar) A woman's breast.
3. •
   (slang, vulgar) A woman's erect nipples, partially masked by clothing.
4. •
   (US, slang) A jewel; especially a diamond.
5. •
   (US, slang) Lysergic acid diethylamide (LSD).