1) cap a genus (family Zygophyllaceae) of tropical American trees and shrubs having pinnate leaves, usu. blue flowers, and capsular fruit
2) any tree or shrub of the genus Guaiacum
3) a resin with a faint balsamic odor obtained as tears or masses from the trunk of either of two trees of the genus Guaiacum (G. officinale or G. sanctum) used formerly in medicine as a remedy for gout or rheumatism and now in various tests (as for peroxidases or bloodstains) because of the formation of a blue color on oxidation see GUAIAC TEST
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Guai·a·cum (gwiґə-kəm) a genus of trees and shrubs of the family Zygophyllaceae, native to tropical regions of the Americas. G. officinaґle L. and G. sancґtum L. are trees found in Haiti and the Dominican Republic whose wood yields the resin guaiac.Medical dictionary. 2011.