The Collaborative International Dictionary of English v.0.48:
Arborical \Ar*bor"ic*al\, a. Relating to trees. [Obs.] [1913 Webster]WordNet (r) 3.0 (2006):
arborical adj 1: of or relating to or formed by trees; "an arborous roof" [syn: arborical, arboreal, arborary, arborous]