from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Pentavalent.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Alternative spelling of quinquivalent.
from The Century Dictionary and Cyclopedia
- In chem., capable of being combined with or exchanged for five hydrogen atoms; having an equivalence of five.
quinque- + -valent (Wiktionary)