tetrad

tet·rad

noun \ˈte-ˌtrad\

Definition of TETRAD

: a group or arrangement of four: as a : a tetravalent element, atom, or radical b : a group of four cells arranged usually in the form of a tetrahedron and produced by the successive divisions of a mother cell <a tetrad of spores> c : a group of four synapsed chromatids that become visibly evident in the pachytene stage of meiotic prophase and are produced by the longitudinal splitting of each of two paired homologous chromosomes