n :  a group or arrangement of four: as  a  :  a tetravalent element, atom, or radical  b  :  a group of four cells arranged usu. in the form of a tetrahedron and produced by the successive divisions of a mother cell <a 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 .
 
 
 
Similar sounding terms:  de·hy·drate  deu·ter·ate  di·hy·drate  dot·ard 
 
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