A phone fart is when you (or the person on the other line) accidentally hits one of the number keys on his/her phone, resulting in a jarring high pitched noise that assaults the ears of both parties.
by Clarin June 18, 2009
When your silent-mode phone vibrates on a hard surface and makes a loud buzzing sound, like flatulence.
by SirSolarSeven November 20, 2015