trigger
noun
a small projecting tongue in a firearm that, when pressed by the finger, actuates the mechanism that discharges the weapon.
Used to describe an action that began in the past, has continued continuously, and is still in progress.
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Not surprisingly, our Science paper has been triggering some unhappy responses.
From Slate ● Oct. 31, 2011