Trimaximal mixing (also known as threefold maximal mixing) refers to the highly symmetric, maximally CP-violating,
where
Originally proposed as a candidate lepton mixing matrix, and actively studied as such (and even as a candidate quark mixing matrix), trimaximal mixing is now definitively ruled-out as a phenomenologically viable lepton mixing scheme by neutrino oscillation experiments, especially the CHOOZ reactor experiment, in favour of the no longer tenable (related) tribimaximal mixing scheme.