nightlyEnglishOxford American Thesaurusnightly adjective 1 we were subjected to almost nightly raids: every night, each night, night after night, night in, night out. ▷antonyms occasional. 2 the badgers' nightly wanderings: nocturnal, nighttime, at night. ▷antonyms daytime.adverb a Tyrolean band plays there nightly: every night, each night, night after night, night in, night out.