Source : Webster's Revised Unabridged Dictionary (1913)

Nightly \Night"ly\, a.
   Of or pertaining to the night, or to every night; happening
   or done by night, or every night; as, nightly shades; he kept
   nightly vigils.

Nightly \Night"ly\, adv.
   At night; every night.

Source : WordNet®

nightly
     adj : happening every night; "nightly television now goes on until
           3:00 or 4:00 a.m."
     adv : at the end of each day; "she checks on her roses nightly"
           [syn: {every night}]