Any person or thing that has a longneck. Most comonly referred to the Diplodocus, a dinosour, which was well known for having a long neck.
Recently, Katniss Everdeen (Jennifer Lawrence) from The Hunger Games has been known for having a long neck. Some people have given her the nickname Katneck Everlong. A mixture of her name and a refernce to her long neck.
Jennifer Lawrence is a longneck.