The Collaborative International Dictionary
Pentabasic
Pentabasic \Pen`ta*ba"sic\, a. [Penta- + basic.] (Chem.) Capable of uniting with five molecules of a monacid base; having five acid hydrogen atoms capable of substitution by a basic radical; -- said of certain acids.
Wiktionary
pentabasic
a. 1 (context chemistry English) (''of an acid'') containing five replaceable hydrogen atoms 2 (context chemistry English) (''of a salt'') having five atoms of a univalent metal