Definition of "firing pin" [fir•ing pin]
1. The part of the bolt or breech of a firearm that strikes the primer and detonates the charge of a projectile. (noun) American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.