It’s an abbreviation of “I HATE BOOP SO MUCH” and if you have to ask what “Boop” means, well then your just gonna have to figure that one out yourself.
Stands for "I hate you so much right now". Usually used when you hate someone at the moment of speaking and you want to inform him/her. Comes from the song Caught Out There performed by Kelis.
You are such lucky bastards every time we play table football! You win again?!?! IHYSMRN!!!!!!!!