Tities so fuking big that they hurt the girl they are a part of. The girl has massive stretch marks on them because they are so damn big. Juggs are tits so big that even the largest cock in the world would get lost in them when performing a titty fuck!
Although commonly used to refer to the female mammary glands, a less used definition applies to 3-5 offsuit in Texas Hold'em. Typically a terrible hand, 3-5 offsuit often seems to make strangely strong hands, usually winning big pots due to it's unexpected nature. "Juggs" is a truncation of juggernaut, the original name for powerhouse hand of 3-5 offsuit.
