STAR does stand for
Start
The
Airline
Right.
At SkyWest (and the policy is most likely much the same across other airlines, but I can only speak for my own), a definition of a STAR flight is a flight of which an aircraft has been on the ground for
over 6 hours.
Usually these flights (of course owing to aircraft utilization to make money) only operate in the morning, the first flights of the day. Any delay in a STAR flight is not good, and there is a degree of accountability required if a STAR delay occurs. For example, SkyWest SFO has only one STAR flight currently, the 0600 CRJ departure to BOI.
STAR flights differ from PRTY (Priority) flights, Priority flights are usually those that are prominent (widebody aircraft, routing of aircraft includes a downline international segment, large connections to international destinations, and aircraft operating international segments).
I may not be spot on with my PRTY explanation, but that's how it was explained to me a while back by someone from United.
Happy Travels!

Kai
-----
SkyWest Airlines - the
world's largest independently-owned regional airline!
The opinions expressed within these posts are the sole opinion of the poster. They do not necessarily reflect the opinions of my employer, SkyWest Airlines, or those of our major partners, United Airlines, Delta Air Lines, or Continental Airlines, respectively.