caffeine Meaning, Definition & Usage

  1. noun a bitter alkaloid found in coffee and tea that is responsible for their stimulating effects
    caffein.

WordNet

Caf*fe"ine noun
Etymology
Cf. F. caféine. See Coffee.
Definitions
  1. (Chem.) A white, bitter, crystallizable substance, obtained from coffee. It is identical with the alkaloid theine from tea leaves, and with guaranine from guarana.

Webster 1913