Pol`y·syn·thet'ic (-sĭn*thĕt'ĭk) adjective [ Poly- + synthetic .] Characterized by polysynthesis; agglutinative. Polysynthetic twinning (Min.) , repeated twinning, like that of the triclinic feldspar, producing fine parallel bands in alternately r... Found on http://www.encyclo.co.uk/webster/P/124