1. simply, it's a Cadillac car that's pink in color.
2. a classic song used as a B-side for Bruce Springsteen's 1984 hit "
Dancing in the Dark". Soon after that hit raced up the charts Pink Cadillac cars became a vogue. The Aretha Franklin hit "Freeway of Love" mentions a pink Cadillac. Bruce's track was covered by Natalie Cole and was a hit for her in 1988. Also the
country rock band
South Pacific made their own cover version. Also in 1989 there was a film by that name, and so on.