Definition - to smell worse than : have a more powerful stench than
Outstink is not one of our most frequently searched-for words, for some reason. Possibly because the action of stinking more than others is not generally a desirable thing. However, this is a useful word, as anyone who has ever, to paraphrase Kris Kristofferson, had to dig through laundry in search of their cleanest dirty shirt can attest.
Thy only sighs are vented at the Bum,
Outstink a Carrion, and outroar a Drum.
— François Rabelais (Trans. by P. M.), The Fifth Book of The Works of Francis Rabelais, 1694