Glossary
Paymaster
An ERC-4337 contract that sponsors gas for a UserOperation — letting users pay in ERC-20 tokens, in fiat off-chain, or have the dApp eat the cost.
A paymaster sits between a smart-contract wallet and the bundler: it agrees to cover the gas for a specific UserOperation as long as its own rules are satisfied. Common shapes include "pay gas in USDC" (the paymaster takes USDC from the user and pays the bundler in ETH), "dApp eats gas" (the paymaster is funded by the dApp), and "verifying paymaster" (off-chain signature gates sponsorship).
Paymasters are what make gas-less and stablecoin-paid UX work in ERC-4337 without changing the underlying protocol.