Longman Dictionary of Contemporary English
The Collaborative International Dictionary
Poly- \Pol"y-\ [See Full, a.] A combining form or prefix from Gr. poly`s, many; as, polygon, a figure of many angles; polyatomic, having many atoms; polychord, polyconic.
Douglas Harper's Etymology Dictionary
word-forming element meaning "many, much, multi-, one or more," from Greek poly-, combining form of polys "much" (plural polloi); cognate with Latin plus, from PIE root *pele- (1) "to fill," with derivatives referring to multitudinousness or abundance (cognates: Sanskrit purvi "much," prayah "mostly;" Avestan perena-, Old Persian paru "much;" Greek plethos "people, multitude, great number," polys "much, plenty," ploutos "wealth;" Lithuanian pilus "full, abundant;" Old Church Slavonic plunu; Gothic filu "much," Old Norse fjöl-, Old English fela, feola "much, many;" Old English folgian; Old Irish lan, Welsh llawn "full;" Old Irish il, Welsh elu "much"); probably related to root *pele- (2) "to spread."\n
\nProperly used in compounds only with words of Greek origin. In chemical names, usually indicating a compound with a large number of atoms or molecules of the same kind (such as polymer).
Wiktionary
pre. 1 many 2 polymer