"Moar" is a misspelt version of "More!", which, according to knowyourmeme.com, MOAR is an expression of interest and desire, indicating the poster wishes more of the same or similar type of content thus provided. It is a counterpoint of "Do not want".
"Moar" usually indicates a demand of seeing more of the similar themes produced, unlike back in the days where 1337speak were all the rage, "Moar" is more of a roar.
In Japanese, it's being defined as "いいぞもっとやれ" (iizo motto yare), literally translated as "Nice, do it more!"
There is no definitive credit to who for the invention of this meme. However in pixiv, the definition of "Moar" applies to these conditions stated below :
*****"No bars hold; open your heart, release the restrictions of your body, and do it more!"*****
Usually, there are cases where illustrations fit in the definition of "Moar", like this:
- If the illustration is meant to be innocent but slipped halfway to the point of no return? MOAR!
- If you can't help but to keep on doing and repeating things that you are NOT supposed to do? MOAR!
In the west, the practical ownership of "Moar" appears to belong to 4chan’s Anonymous, where the term is most commonly found.
As well, this tag is usually related to seme uke relationships...be it yaoi or yuri otherwise.