Wordnet 3.0
ADJECTIVE (1)
1. 
 (poetic) still or calm; 
- Example: "in the stilly night"
The Collaborative International Dictionary of English v.0.48:
Stilly \Stil"ly\, adv.
   In a still manner; quietly; silently; softly. --Dr. H. More.
   [1913 Webster]
         The hum of either army stilly sounds.    --Shak.
   [1913 Webster]
The Collaborative International Dictionary of English v.0.48:
Stilly \Still"y\, a.
   Still; quiet; calm.
   [1913 Webster]
         The stilly hour when storms are gone.    --Moore.
   [1913 Webster]
WordNet (r) 3.0 (2006):
stilly
    adj 1: (poetic) still or calm; "in the stilly night"