The Collaborative International Dictionary
Quinque-
Quinque- \Quin"que-\ [L. quinque five. See Five.] A combining form meaning five, five times, fivefold; as, quinquefid, five-cleft; quinquedentate, five-toothed.
Douglas Harper's Etymology Dictionary
quinque-
before vowels quinqu-, word-forming element meaning "five, having five," from Latin quinque "five," by assimilation from PIE *penkwe (see five).
Wiktionary
quinque-
pre. five