xylarium UK /zaɪˈlɛəɹi.əm/US /zaɪˈlɛɹi.əm/ noun1 •A herbarium specialising in specimens of wood.A plant anatomist receiving such samples can remove pickled wood and bark for anatomical study, then dry the remaining portions for inclusion in a xylarium. — 1996 formsxylaria · xylariums