When a person (usually an exotic entertainer) places an amount of glitter into his/her rectum and then flatulates a sparkling cloud onto another person. This service is usually performed for a fee in addition to the normal tip.
"Scott" got a unicorn kiss from the cowboy at Gloria's on his bachelor party, but he was so drunk, he still doesn't' know.
A unicorn kiss is where you get down on your hands and knees and tuck your dick back between your thighs. Your partner enters you anally with a strap-on attached to his\her forehead and gives you a blowjob at the same time.