A lepton is a type of subatomic particle. The corresponding antiparticle is the antilepton. The leptons are actually a group of associated particles, including the muon, electron, positron, and types of neutrinos.
In 2373, Commander William Riker used leptons to counteract a Cardassian ship's attempt to block subspace communication through the use of antileptons. The resulting interaction blinded the Cardassian sensors. (TNG - Slings and Arrows eBook: A Weary Life)