starting gate

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

• noun A series of stalls with doors that open simultaneously at the beginning of a race.
• noun A movable barrier that starts an automatic timer when a competitor, such as a skier, moves through it.

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

• noun a movable barrier on the starting line of a race course