Jack is a versatile word that has multiple meanings and synonyms. As a noun, it can mean a male given name, a small machine or tool, or a playing card bearing the picture of a knave or servant. The synonyms for jack in this sense include device, gadget, card, or knave. As a verb, it can mean to lift something using a device or to steal. In this context, its synonyms include hoist, raise, or filch. Jack can also mean a type of fish or a small flag flown at the front of a ship. In this context, its synonyms include fish species names or pennant.