Shipping, derived from the word relationship, is the belief that two characters, fictional or non-fictional, would be interesting or believable (or are, or will be, or should be) in a romantic relationship. It is considered a general term for fans' emotional involvement with the ongoing development of romance in a work of fiction. Though technically applicable to any such involvement, it refers chiefly to various related social dynamics observable on the Internet, and is seldom used outside of that context.
Shipping can involve virtually any kind of relationship – from the well-known and established, to the ambiguous or those undergoing development, and even to the highly improbable and the blatantly impossible.
SulBala are impossible now that Madhu and RK are officially a couple but still SulBala can be shipped even if they aren't official