(Science: chemistry) Pertaining to, or designating, a dibasic acid of the oxalic series found in archil (Roccella tinctoria, etc), and other lichens, and extracted as a white crystalline substance C17H32O4.
Origin: F. Roccellique, fr. Roccelle archil, It. & NL. Roccella, fr. It. Rocca a rock, because archil grows on rock.