what do you mean by decomposing? lol
I'll answer for him, as he may be otherwise occupied. This is what he means (I'm pretty sure):
Rotting in the ground. It's a pun, a play on words. It's meant to be a joke, to be funny. These types of jokes aren't always understood by people who aren't native English speakers.
It's a play on 'compose' and 'decompose'.
It's not the first type of pun like this. In fact, if you go way back to Shakespeare's 'Romeo and Juliet', you'll learn that Mercutio is killed. As Mercutio is dying, he turns to Romeo and says, "Ask for me tomorrow, and you shall find me a grave man".

