Caffeine - definition from Biology-Online.org
[(Science: chemical) a xanthine derivative that elevates camp levels in cells by inhibiting phosphodiesterases. a bitter alkaloid found in coffee and tea that is responsible for their stimulating effects.Caffeine is a diuretic that stimulates the central nervous system, and can be found in cocoa beans.
MediLexicon caffeine - Medical Dictionary Definition for Term 'caffeine'
[1. An alkaloid obtained from the dried leaves of Thea sinensis, tea, or the dried seeds of Coffea arabica, coffee; used as a central nervous system stimulant, diuretic, circulatory and respiratory stimulant.