Stablecoin
A cryptocurrency designed to hold a constant value against a currency, usually the US dollar, through reserves or an algorithm. De-pegging can be abrupt.
Definition
A stablecoin is a crypto asset whose goal is to hold a peg to a currency (1 USDT ≈ 1 USD, for example). Collateralised stablecoins are backed by reserves (cash and bonds, or over-collateralisation in crypto); algorithmic ones rely on a supply mechanism. A de-peg is a break away from the reference currency, and it can be sudden and deep.
Example
Most transfers between exchanges and most “parking” of funds in crypto happens through stablecoins. Under market stress the exit liquidity can be thinner and the spread wider — check the depth of the market before you treat “stable” as safe money.
Anti-example / common mistake
Treating a stablecoin like a “bank” or a “deposit account”. It is an operating tool (liquidity, transfers), not a guarantee of value. Safe holding is what a fiat bank account is for.