Wordnet 3.0
ADVERB (1)
1. 
 in an unnatural eery manner; 
- Example: "it was eerily quiet in the chapel"[syn: eerily, spookily]
WordNet (r) 3.0 (2006):
spookily
    adv 1: in an unnatural eery manner; "it was eerily quiet in the
           chapel" [syn: eerily, spookily]