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.

happening every night; "nightly television now goes on until 3:00 or 4:00 a.m."

At night; every night.

at the end of each day; "she checks on her roses nightly"

a daily compilation of Firefox that implements all patches and updates that were fixed that day

A Moodle Nightly is built automatically every day from the most recent code, and is available from the Moodle web site. It can be useful if you don't have CVS, but you want to try the latest features. It can also contain bugs, since they haven't been well-tested.

a test case that must be run every time there is a new build