Aerenchym \A"["e]r*en`chym\, Aerenchyma \A`["e]r*en"chy*ma\, n. [NL. a["e]renchyma. See {A["e]ro-}; {Enchyma}.] (Bot.) A secondary respiratory tissue or modified periderm, found in many aquatic plants and distinguished by the large intercellular spaces.