Cryptocurrency projects often lock a part of the token’s supply and release it gradually to prevent early investors and insiders from selling in large quantities immediately after they get the allocations. When the tokens are unlocked, they become available to sell, and thus, such events are usually considered bearish; often they induce price drops. However, sometimes investors front-run and may sell before the unlocking happens.
Source: https://www.coindesk.com/markets/2023/09/25/optimism-slumps-most-among-crypto-majors-ahead-of-30m-token-unlock/?utm_medium=referral&utm_source=rss&utm_campaign=headlines