Used to describe a person that has had sex with many people, thus causing a spread in sexual viruses within the workplace, or even community.
Health teacher: "Don't be a jumping johnny!";"you'll get an STD".
an incredibly versitile alegory refering to the sexual nature of a duke in the seventeenth century royal court.
Rick bowed before his wife, unbeknowst to her, he was reveling in thoughts common to a johnny jump-up