The Collaborative International Dictionary of English v.0.48:
Albedo \Al*be"do\, n. [L., fr. albus white.] Whiteness. Specifically: (Astron.) The ratio which the light reflected from an unpolished surface bears to the total light falling upon that surface. [1913 Webster]WordNet (r) 3.0 (2006):
albedo n 1: the ratio of reflected to incident light [syn: albedo, reflective power]