A shortened mission is one that is complete on an earlier date than originally scheduled.
STS-2 - Nov. 12-14, 1987
The mission was shortened by approximately three days due to a failure of the number one fuel cell.
STS 51-I - Aug. 27 - Sept. 3, 1985
Mission was shortened one day due to a problem with one of the payloads, the AUSSAT satellite, which resulted in its being deployed earlier than scheduled.
STS-35 - Dec. 2 - 10, 1990
Mission was cut short one day due to impending weather at the primary landing site, Edwards Air Force Base, California.
STS-44 - Nov. 24 - Dec. 1, 1991
The mission was originally scheduled for 10 days, but was cut short due to on-orbit failure of one of three orbiter inertial measurement units.
STS-83 - April 4 - 8, 1997
The 16-day mission was shortened after the malfunction of fuel cell number two.