Wiktionary
vb. 1 (context idiomatic slang English) To ride in the front passenger seat of a vehicle, next to the driver. 2 (context idiomatic slang figuratively English) To accompany someone in order to assist and protect.
Usage examples of "ride shotgun".
But if he was riding to see him, it must be to tell him of the gold shipment and the fact that Matt was to ride shotgun.
And now I don't have anybody to ride shotgun while I mow the strip.
Mildred was going to ride shotgun, so she wouldn't have to use her sprained foot for driving the whole way.
Of the Five Barons, Hardcoe was the only one who organized sec parties to ride shotgun on trade caravans.
Two miners would ride shotgun on the buggy itself, one watching out the back while the other sat in front beside Zach.
I was going to ride shotgun on a gold shipment, and I had better do it in style.