A rug pull is an exit scam where the team behind a project removes all liquidity or funds from the protocol and abandons it. The term comes from "pulling the rug out" from under investors. Rug pulls typically happen on memecoins and unaudited DeFi forks within hours or days of launch, but can also be slow-motion drains over weeks.
Classic indicators: anonymous team, no audit, locked dev tokens with short or no vesting, control of liquidity pool LP tokens not renounced or timelocked, sudden unannounced contract upgrades, social media accounts created within 30 days of launch.