Glossary
Child-Pays-For-Parent (CPFP)
A Bitcoin technique to accelerate a low-fee transaction by spending one of its outputs in a child transaction that pays a high fee for the pair.
CPFP exploits how miners select transactions. If a parent transaction is stuck (low fee), the recipient (or sender, if they control a change output) can broadcast a child transaction that spends one of the parent's outputs and pays a fee high enough that the combined fee/weight of parent+child is attractive to miners.
The child cannot be mined without the parent — so a rational miner includes both. CPFP is the standard recovery path when you cannot RBF your own transaction (e.g., because you no longer hold the input keys).