It's when you love someone more than they love you even though they used 'mostest'.
In most cases, 'mostest' can't be beaten, but there are always special exceptions, such as 'I love you more than mostest'
Person 2. : *oh damn what do I say I can't accept this because it isn't true!!!* I love you more than mostest.
Person 1 : Shucks, you got me there. I'll have to accept your love then
sean: i love you.
shannon: i love you too.
sean: i love you more.
shannon: i don't think so.
sean: umm...yep..lemme check urban dictionary...yeah, it says i do.