It means that you're giving a blowjob to someone with a thick and girthy dick. It's the sister meaning of deepthroat. It can be from a chode, to a cucumber.
Becky: OMG STEPHANIE, I JUST GAVE JUAN THE BEST WIDETHROAT ANYONE COULD'VE GIVEN HIM. HE HAS THE THICKEST DICK I'VE SEEN.
by StultifiedJohnny July 23, 2017