(covers information from several alternate timelines)
The ship's in pieces and we've got less than a skeleton crew aboard!"
skeleton crew featured a minimal number of crewmen required for starship or space station operations, sometimes fewer. Skeleton crews were often formed during emergencies.
D5-class variant was capable of operating with a skeleton crew of just four. ( : " ENT ")
The final version of the
Xindi weapon was designed to be operated by a skeleton crew. ( : " ENT ")
Azati Prime In
2258 of the alternate reality, Khan Noonien Singh informed James T. Kirk that USS had been modified to allow for a minimal crew. He later reiterated this when Vengeance Montgomery Scott asked where the crew was, adding that it could be flown by one person if need be. ( ) Star Trek Into Darkness
2268, the USS needed a skeleton crew of twenty while using the Enterprise M-5 multitronic unit. ( : " TOS ")
The Ultimate Computer
2287, Starfleet Command had the USS go to Enterprise-A Nimbus III, much to Captain Montgomery Scott's dismay as he remarked, " The ship's in pieces and we've got less than a skeleton crew aboard!" ( )
Star Trek V: The Final Frontier
2368, Lieutenant Commander Data suggested a skeleton crew from the USS could take the Enterprise-D to a Kallisko starbase. ( : " TNG ")
2369, a skeleton crew operated the space station Deep Space 9 after an aphasia virus infected everyone except Quark and Odo. ( : " DS9 ")
The term was not spoken in the episode but is in the script for the episode. 
2370, the Enterprise-D was left with only a skeleton crew under the command of Beverly Crusher while the rest of the crew were on the surface of a planet, searching for Data. ( : " TNG ", " Descent ")
Descent, Part II
A few weeks later, a skeleton crew was left to run Deep Space 9 during a
plasma disruption that forced the evacuation of the station. ( : " DS9 ")
2373, when members of the USS crew were replaced with Voyager Nyrians via translocation, the ship was eventually left with only a skeleton crew, with Commander Chakotay as the last remaining officer before he, too, was removed from the ship. ( : " VOY ")
Reckoning began on Deep Space 9 in late 2374, a skeleton crew remained aboard once the majority of the station's population had left. ( : " DS9 ")
2375, when Ensign Marla Gilmore spoke to Commander Chakotay of leaving the USS in favor of the USS Equinox Voyager, Chakotay noted that the Equinox was already operating with a skeleton crew. The vessel had, in fact, lost half of its original crew shortly after its arrival in the Delta Quadrant. ( : " VOY ")
Several scripts described small numbers of crew seen working as "skeleton crews". These episodes include : " TOS " as well as the The Menagerie, Part I Star Trek: Deep Space Nine installments " ", " Babel ", " In the Hands of the Prophets ", " The Collaborator ", and " The Visitor ". Similarly, in a line of unused dialogue from the script of The Assignment : " TOS ", Shore Leave Yeoman Tonia Barrows reported, "
Skeleton standbys are set up to relieve the