A slang word derived from 'relationships' that generally means people who support certain relationships in fanfiction. It is a common joke to say that you sail on a certain ship. Most commonly identified with the Harry Potter fandom.
Fanfics revolving around a certain relationship.
When you feel as if you are on a boat (ie rocking from side to side) when you are not or when you get a feeling the same as when a lift begins to drop when you are actually on normal ground.
It does exist.... there is no cure.
* These videos are coming directly from Youtube, they may or may not be most relevant to the word "Shippers"