Mostesterest means the biggest amount of something, and is used to end an argument with no complaints.
E.g Tiffin said 'I miss you' Ryan said 'I miss you most' Tiffin replied 'Well I miss you the moster' and Ryan concluded with 'No I miss you the mostesterest' and dominated the conversation.
A completely made-up, exaggerated, and absolutely unbeatable superlative used to win emotional battles or expressions of affection. It goes beyond “most,” “mostest,” and even “mostester.” The final, ultimate trump card in any emotional face-off Olympics.
How to use it:
Friend 1: I love fries.
Friend 2: I love fries too.
Friend 1: I love fries more.
Friend 2: I love fries the most.
Friend 1: I love fries the mostesterest. Boom.