Mnemonic (I dey laugh o) for a Pidgin English phrase (which translated to English means "I'm laughing as well") made popular by former Nigerian President Olusegun Obasanjo.

IDLO is a scornful and mocking response to another's position on a subject. IDLO has been made popular by young Nigerians who usually respond to a comment on social networks such as Facebook and Twitter with the pithy "IDLO"

Literally everyone, ever. Including the writer of this definition.