Wiktionary
pack heat
vb. (context idiomatic English) To carry one or more handguns on one's person, especially in a concealed manner.
Usage examples of "pack heat".
There was once a time when morticians and their assistants didn't pack heat.
FBI agents are allowed to pack heat on commercial airlines, and let me hasten to add, it wasn't armed civilians who mistakenly shot down Randy Weaver's wife, child, and dog.