What does "fall out" mean?

To have a serious disagreement with someone that causes a breakdown in the relationship. To "fall out" with someone is more than just an argument, it implies a lasting rupture, at least temporarily. When you fall out with a person, something has been damaged between you, and the friendship or working relationship cools down as a result.

"They fell out over money and haven't spoken since."
"We fell out last year but we've made up now."
"She fell out with her sister just before the wedding, which made the whole day awkward."
"Don't fall out with your neighbours over something so small."

Notice that we use the preposition "with" for the person and "over" or "about" for the reason. You fall out WITH someone OVER something.

How serious is it? More serious than an argument, less permanent than a complete break. People who fall out can and often do reconcile. Think of it as a wound rather than an amputation. The relationship is hurt but not necessarily ended forever. This is why we can happily say "we fell out but we've made up now."

The consequences or negative effects of an event. "The fallout from the announcement affected the whole team." This is a separate but related use, it comes from nuclear fallout, the widespread effects of a blast. The image is of harmful particles settling over a wide area long after the explosion itself.

"The political fallout lasted for months."
"There was a lot of fallout after the two directors resigned."

Students often confuse the verb form and the noun form. Remember that the verb is two words with a person after it, "to fall out with someone," while the noun is one word describing consequences, "the fallout." Saying "we had a fall out" mixes the two up. Use "we had a falling out" instead.

Picture two friends standing close together, then imagine one of them "falling out" of the friendship, dropping away and leaving a gap between them. The physical image of someone falling away helps you remember that the relationship has opened up a distance.

• "We fell out" - British English, implies a rift
• "We had a falling out" - American English equivalent
• "We had a big argument" - neutral
• "We've had a row" - British, informal (the "row" here rhymes with "cow," not with "low")

In casual conversation among friends and family, "fall out" is extremely common and sounds natural. "Me and Dave have fallen out again" is everyday speech. In a formal workplace setting, native speakers often soften it or choose something more neutral. You might hear "there's been some tension between the two teams" or "they've had a disagreement" rather than the blunter "they've fallen out." The phrasal verb is not rude, but it is direct, so more diplomatic wording is often preferred in professional emails and meetings.

The opposite of falling out is "to make up," which means to reconcile and repair the relationship. "They fell out on Monday but made up by Friday." You may also hear "to patch things up," which means to fix a relationship after a disagreement. "We patched things up over a coffee." Another close relative is "to have a falling out," the noun version already mentioned, which describes the whole event rather than the action. Learning these together gives you a full toolkit for talking about relationships that break and then mend.

Used well, "fall out with someone" lets you describe a very human situation in a compact, natural way. Just remember the prepositions, keep the verb and noun forms separate, and choose a gentler phrase when the setting is formal.