Definition of pyrenes:
(n) :
(chemistry) A polycyclic aromatic hydrocarbon containing four fused benzene rings; first isolated from coal tar
(adj) :
(relational, obsolete) Of or pertaining to the Pyrenees, a range of mountains separating France and Spain; Pyrenean.
(n) :
(botany) Alternative form of pyrena. [(botany) A nutlet resembling a seed, or the stone of a drupe, comprising the endocarp and the kernel.]