Ninja shopping
Going to a large shop or store, typically a supermarket and getting in and out really quickly. To just buy what you were going in for without getting delayed by special offers or little old ladies getting in the way.
Max was out of the store with the beers before they guys had even found a good parking spot. Thats why they sent him, he was the best at ninja shopping.
Shopping Ninja
When the person you're shopping with randomly disappears with the shopping cart with out you noticing. You usually spend the rest of the shopping trip looking for them.
Jack: Yo Sally have you seen mom?
Sally: She pulled a shopping ninjas on me.
Sally: She pulled a shopping ninjas on me.