Prrrent
Pronounced with rolled r's, Prrrent is the approximate sound that is made by flatulence. Scientists have determined that this is the most accurate onomotopeia for this action, and is included in many top dictionaries to describe the sound.
Girl: *farts*
James: That sounded like Prrrent!!!
*Many Lolz*
James: That sounded like Prrrent!!!
*Many Lolz*