Leaches off is a phrasal verb which means to derive benefits from someone or something without giving anything in return. The synonyms for leaches off include mooches, sponges, freeloads, parasites, and scrounges. Mooching means to ask for or obtain something without intending to return it or compensate for it. Sponging means to obtain something for free or by relying on the generosity of others. Freeloading means to receive or take advantage of something without paying for it. Parasite describes a person who lives off or takes advantage of someone else's resources. Scrounging means to obtain something through scavenging or hustling. All these words are used to describe someone who takes advantage of others without giving anything in return.