a mechanical or electrical explosive device or a small amount of explosive; can be used to initiate the reaction of a disrupting explosive(noun.artifact)
Example: We had to cap the number of people we can accept into our club.
source: wordnet30
To cover with a cap, or as with a cap; to provide with a cap or cover; to cover the top or end of; to place a cap upon the proper part of; as, to cap a post; to cap a gun.(verb)