1.nounA pointed instrument of the dagger kind fitted on the muzzle of a musket or rifle, so as to give the soldier increased means of offence and defence. Originally, the bayonet was made with a handle, which needed to be fitted into the bore of the musket after the soldier had fired.
2.nounA pin which plays in and out of holes made to receive it, and which thus serves to engage or disengage parts of the machinery.