High-Priority Transaction, Free Tx
This definition comes from the technical glossary.
Definition
Transactions that don’t have to pay a transaction fee because their inputs have been idle long enough to accumulated large amounts of priority. Note: miners choose whether to accept free transactions.
Synonyms
- 
    High-priority transaction 
- 
    Free transaction 
Links
- 
    High-priority transactions — Developer Guide 
- 
    Free transaction relay policy — Bitcoin Wiki