“Outcomes that are not the ones foreseen and intended by a purposeful action.” (related: collateral damage — “Deaths, injuries, or other damage inflicted on an unintended target.”, Goodhart’s law — “When a measure becomes a target, it ceases to be a good measure”; Campbell’s law; Streisand Effect — “The phenomenon whereby an attempt to hide, remove, or censor a piece of information has the unintended consequence of publicizing the information more widely, usually facilitated by the Internet”; cobra effect — “when an attempted solution to a problem actually makes the problem worse.”; “Kick a hornet’s nest.”)
Source:
Gabriel Weinberg’s Mental Models I Find Repeatedly Useful