Liquidation is the broker's forced exit of your positions when your account no longer has enough equity to maintain them. It is the operational consequence of a margin call that wasn't met — or, in modern crypto and futures venues, an automated process that triggers the moment your account hits the liquidation threshold without human review.
In crypto perpetuals, liquidation is the central risk most retail traders underestimate. A 10× leveraged long with a 10% drop in the underlying results in a complete account wipeout — the position is liquidated at the moment unrealized losses match the posted collateral, with no opportunity to add funds, hedge, or wait for a bounce. The exchange's insurance fund and auto-deleveraging mechanisms can extend the damage in extreme moves.
Futures markets behave similarly through the daily settlement and variation margin process. Your account is marked-to-market every day; losses are debited that night, and if your account drops below maintenance, the broker initiates liquidation the next morning regardless of how strongly you believe the move was overreaction.
Cash stock accounts are mostly insulated from forced liquidation as long as you're not using margin — your worst case is the position going to zero, which takes time and gives you the option to exit on your own terms. The moment you cross into margin-funded positions, leveraged ETFs, options-on-margin, or any of the derivative venues, liquidation risk is now a real failure mode. The math of liquidation is uncompromising: you don't get to wait for the trade to come back, because the broker took the decision out of your hands at exactly the wrong moment.