Piggyback means riding on someone's back with your arms around their shoulders and your legs around their waist. When you were younger, you probably got piggyback rides from your parents when your legs got tired at the park or zoo. The person giving the ride leans forward slightly while you hold on, and they support your weight by hooking their arms under your knees.

The word also describes doing something by attaching it to or building upon something else that's already happening. A spacecraft might piggyback on a rocket to reach orbit. A small company might piggyback on a larger company's delivery system to save money. When your school adds a field trip onto a day when buses are already scheduled, that's piggybacking on existing transportation plans.

In technology, devices can piggyback data by sending information along with other signals. Think of it like slipping a note to your friend inside a book you're already passing to them: you're using something that's already moving to carry something extra.

What matters is the image: something small being carried along by something larger and stronger, making the journey easier.