night shift

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A group of employees working during the night in a factory or business.
• noun The period of time for such work.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A regularly scheduled period of work, during evening or night hours, especially 4 PM to midnight or midnight to 8 AM.
• noun A group of workers who work during the night.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun workers who work during the night (as midnight to 8 a.m.)
• noun the work shift during the night (as midnight to 8 a.m.)