Definitions for: Penta-

Webster (1913) Definition: Pen"ta- [Gr. ?, a later combining form of ? five. See
Five.]
1. A combining form denoting five; as, pentacapsular;
pentagon.

2. (Chem.) Denoting the degree of five, either as regards
quality, property, or composition; as, pentasulphide;
pentoxide, etc. Also used adjectively.