A simple pistil or one element of a compound pistil WordNet 3.0 & Open English WordNet

A discrete organ in the center of a flower capable of receiving pollen and producing a fruit. OmegaWiki

One of the individual female reproductive organs in a flower. A carpel is composed of an ovary, a style, and a stigma, although some flowers have carpels without a distinct style. In origin, carpels are leaves (megasporophylls) that have evolved to enclose the ovules. The term pistil is sometimes used to refer to a single carpel or to several carpels fused together. Wiktionary

Structural unit of a pistil. Wiktionary (translation)