What is the meaning of Piggyback?

On somebody's back or shoulders.

Pertaining to transportation of goods where one transportation unit is carried on the back of something else. For example, a truck on a train.

Attached or appended to something larger or more important.

On somebody's back or shoulders.

To carry (someone) on the back or shoulders.

To attach or append something to another (usually larger) object or event.

To obtain a wireless internet connection by bringing one's own computer within the range of another's wireless connection without that subscriber's permission or knowledge.

To utilize "last-mile" wiring rented from a larger owner ISP by a smaller ISP.

To transport (a lorry/truck) on a flatbed railway wagon.

To enter a secured area at the same time along with (someone having authorized access); to tailgate. (Can we add an example for this sense?)

A ride on somebody's back or shoulders.

An act or instance of piggybacking.

The connection of one intravenous drip to another.

Source: wiktionary.org