The idea that there is a romantic relationship, rather than friendship, between the two men has a large group of fans and followers writing Snucius fan fiction, drawing fan art, and shipping the pairing.
As is common practise in shipping, Snucius is a word put together by Severus' and Lucius' first names. It is a not very popular, but often used, term describing the two men and their relationship. However, most (more than 50% according to polls) fans of the ship prefer to refer to them as Severus/Lucius or Snape/Lucius.
I adore Snucius, they are both so gorgeous.
The Snucius ship has fewer followers than those of the Snupin (Lupin/Snape).