A build of a software program with the latest changes, released every night.
"The development team relies on the nightly build to test their latest code updates before deployment."
"The daily commute is his nightly routine, but tonight he stayed home to read instead."
Happening or appearing in the night; night-time; nocturnal.
"The fireflies danced a nightly ritual over the meadow."
In plain English: Nightly means something that happens every single night without fail.
"We check out our favorite restaurant every night for dinner."
Usage: Use nightly as an adjective to describe something that occurs during the evening hours rather than at any time before dawn. When referring specifically to daily updates like software builds, it functions adverbially to mean "every night."
Every night.
"The alarm clock is set to ring nightly at 6:00 AM."
From Middle English nyȝtly, nihtlich, nihtlic, from Old English nihtlīċ, nihtelīċ ("nocturnal, nightly, of the night, at night"), equivalent to night + -ly. Cognate with Scots nichtlie ("nightly"), West Frisian nachtlik ("nightly, nocturnal"), Dutch nachtelijk ("nightly, nocturnal"), German nächtlich ("nocturnal, nightly"), Danish natlig ("nightly"), Swedish nattlig ("nightly, nocturnal").