oxymoron

An oxymoron is a figure of speech that combines contradictory terms. Oxymorons appear in a variety of contexts, including inadvertent errors such as ground pilot and literary oxymorons crafted to reveal a paradox.

Uttara Gupta: Hahahaha! Let me repeat myself, it's MY wall!
Rohan: Thats an oxymoron

As you might notice the usage of MY, which is a form of the possessive case of I used as an attributive adjective, with Wall which refers to the very public Facebook wall is quite moronic and in this case oxymornonic.