Filthy Robitussin Share definition Flag the act of coughing in one's vagina Xavier: I gave your mother a filthy robitussin on 4:20. Gibbsr: dang. Filthy Robitussin by Christian Gibbs July 30, 2008 0 0 Get merch Get the Filthy Robitussin mug. Buy Now — $32.95 See more merch