There were not eyewitnesses who saw him pull the trigger of the gun.
When you release the trigger on this glue gun, it dispenses glue.
WordNet 3.0 Sense Numbers: 1, 2
The assassination of the Archduke was the trigger that set of World War I.
The dry brush acted like a trigger for the forest fire.
The bank defaults were the initial trigger of the short-term credit crunch.
WordNet 3.0 Sense Numbers: 3