• Piggy-back (transportation), something that is riding on the back of something else
• Piggybacking (security)
  Piggybacking (security)
  In security, piggybacking refers to when a person tags along with another person who is authorized to gain entry into a restricted area, or pass a certain checkpoint. The act may be legal or illegal, authorized or unauthorized, depending on the circumstances...
  
  , when an authorized person allows (intentionally or unintentionally) others to pass through a secure door
• Splash cymbal piggybacking, mounting a cymbal on top of an already stand-mounted cymbal
• Piggybacking, a practice in which a person with bad credit uses the seasoned trade line
  Seasoned trade line
  Aseasoned trade line is a line of credit that the borrowerhas held open in good standing for a long period of time,typically at least 2 years...
  
   of credit of someone else
• Piggyback plant, Tolmiea menziesii
• Piggy-back (law)
  Piggy-back (law)
  Piggy-back applies to contractual agreements in law, more specifically shareholder selling rights. To apply, the piggy-back clause MUST be included in the corporation's shareholder agreement, which is part of the incorporation materials....
  
  , shareholder selling rights
• A technique used in astrophotography
  Astrophotography
  Astrophotography is a specialized type of photography that entails recording images of astronomical objects and large areas of the night sky. The first photographs of an astronomical object were taken in the 1840s, but it was not until the late 19th century that advances in technology allowed for...
  
  

Telecommunications

• Piggybacking (data transmission)
  Piggybacking (data transmission)
  Piggybacking is a bi-directional data transmission technique in the network layer . It makes the most of the sent data frames from receiver to emitter, adding the confirmation that the data frame sent by the sender was received successfully...
  
  , a bi-directional data transmission technique in network layer, sending data along with ACK called Piggybacking
• Piggybacking (Internet access)
  Piggybacking (internet access)
  Piggybacking on Internet access is the practice of establishing a wireless Internet connection by using another subscriber's wireless Internet access service without the subscriber's explicit permission or knowledge. It is a legally and ethically controversial practice, with laws that vary by...
  
  , obtaining wi-fi access by bringing one's own computer within the range of another subscriber's service

Other

• Piggyback circuit breaker
  Circuit breaker
  A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow...
  
  , a double-switch that fits in a single slot in a breaker panel. This is only if they are side-by-side in the same unit — it does not count single half-height units which share a slot. Both are used when a panel has run out of slots, but can still accept the current. The piggyback breaker has two separate outputs, one for each circuit
• Piggybacked contact lens, using a smaller, rigid contact lens on top of a larger, soft contact lens for clinical reasons
• Piggybacking (intravenous therapy), a second infusion set onto the same line
• Piggyback marketing, used to reduce risk, and more established companies can leverage the brand and market reach of a partner to help them very quickly pick up the credibility and awareness needed in new market segments
• Piggyback registration, when owners of restricted stock
  Restricted stock
  Restricted stock, also known as letter stock or restricted securities, refers to stock of a company that is not fully transferable until certain conditions have been met. Upon satisfaction of those conditions, the stock becomes transferable by the person holding the award.One type of restricted...
  
   in a public company are allowed to participate in a public offering underwritten by another party
• "Piggyback", a 2010 TV commercial for T-Mobile USA
  T-Mobile USA
  T-Mobile USA, Inc. is an American mobile-network operator, headquartered in Bellevue, Washington, that provides wireless voice, messaging and data services in the United States, Puerto Rico and the U.S. Virgin Islands. The company is the fourth-largest wireless carrier in the U.S. market with 33.73...