guaiacum n medicinal resin from the lignum vitae tree n hard greenish-brown wood of the lignum vitae tree and other trees of the genus Guaiacum n small genus of evergreen resinous trees or shrubs of warm and tropical America Usage(s) They finally found what they wanted in gum guaiac, made from the sap of the tropical American guaiacum tree. Synonym(s) lignum vitae guaiac Guaiacum genus Guaiacum