indiscretion
A careless mistake in what you say or do.
An indiscretion is a lapse in judgment where someone does or says something unwise, inappropriate, or embarrassing. It's the kind of mistake that makes you think, “I really shouldn't have done that.” When a friend accidentally reveals a secret you told them in confidence, that's an indiscretion. When someone shares an embarrassing story about another person at a party, that's an indiscretion too.
The word suggests a momentary failure to think things through or consider the consequences. Maybe you blurt out a comment about someone's outfit without realizing they're standing right behind you. Maybe you forward a private message to the wrong group chat. These moments of indiscretion usually aren't intentionally mean or malicious. They're just poorly thought out.
Adults often use this word when discussing social or professional mistakes: a politician's indiscretion might be an inappropriate comment caught on camera, or a lawyer's indiscretion might be discussing a client's private information at a restaurant where others can overhear. The opposite quality, discretion, means being thoughtful, tactful, and careful about what you say and do. Someone who shows discretion knows when to speak up and when to keep quiet, when to share and when to protect someone's privacy.