The Oxford Thesaurus An A-Z Dictionary of Synonyms - nightly adj.

1) every night, each night, each and every night, night after night: The watchman does his nightly rounds. 2) night-time, nocturnal, bedtime: A nightly glass of warm milk promotes sound sleep. --adv. 3) every night, each night, nights, after dark, after sunset; nocturnally: The bird sings nightly outside my window.