Maddy: I love you, Hannah.
Hannah: I love you too!
Maddy: I love you more!
Hannah: But, I love you most...
Maddy: I love you mostest, though.
Hannah: I LOVE YOU MOSTESTESTEST.
To love someone more than anything that exists or has ever existed. This is more than most and cannot be beaten, under any circumstances, especially by the non-existent words "mostestest" and "mostestestest"
You add mostest at the end if I love you to signify you love your partner the mostest of all. Whoever says I love you mostest automatically loves the other partner more than he or she does forever and HAS to accept.