[guai.a.cum] n [NL, fr. Sp guayaco, fr. Taino guayacan] (1553) 1: any of a genus (Guaiacum) of the caltrop family of tropical American evergreen trees and shrubs having pinnate leaves, usu. blue flowers, and capsular fruit
2. a: the hard greenish brown wood of a guaiacum (esp. Guaiacum officinale) b: a resin with a faint balsamic odor that is obtained from the trunk of two guaiacums (G. officinale and G. sanctum) and often used as a clinical reagent