The Collaborative International Dictionary of English v.0.48:
Passively \Pas"sive*ly\, adv. 1. In a passive manner; inertly; unresistingly. [1913 Webster] 2. As a passive verb; in the passive voice. [1913 Webster]WordNet (r) 3.0 (2006):
passively adv 1: in a passive manner; "he listened passively" [ant: actively]