The part of your pants or shorts around the crotch and zipper where excess zipper and fabric material fold outward forming a bulge, resembling a mountain, or even a boner; though both males and females are often victims of jessica's mountain. Jessica's mountain can usually be seen when one is sitting down.
austin d: dude josh, do you have a boner?
josh a: naw man thats just my jessicasmountain
The coolest and funniest person you'll ever fucking meet. Usually a girl and also fucking beautiful and smart and amazing at everything (especially fencing). If you know a Jessifus you should be proud and thankful that she accepts you as a friend.