octamethylcyclotetrasiloxane
/ˌɒktəmɛθʌɪlˌsʌɪkləʊtɛtrasɪˈlɒkseɪn/Chemistry
noun
A colourless oily liquid compound with a cyclic tetrameric structure, [(CH3)2SiO]4, that is an intermediate in the manufacture of many silicones.
Origin
1940s. From octa- + methyl + cyclo- + tetra- + siloxane.