Find the appropriate meaning of the underlined idiom. When he was speaking,…

Concept

An idiom is a fixed expression whose overall meaning cannot be worked out from the literal meaning of its individual words. The phrasal idiom "to cut someone off" has more than one sense, so the correct sense must be chosen from the surrounding context. When it is used about a person who is talking, "to cut someone off" means to stop them mid-speech — that is, to interrupt them before they have finished.

Application

In the sentence "When he was speaking, his father cut him off," the time clause "When he was speaking" tells us the action happened while the son was in the middle of talking. The father broke into the son's speech and stopped him from continuing. That is exactly the speech-related sense of the idiom, so "cut him off" here means interrupted him.

Why the other meanings do not fit here

• "Disinherited him" — "cut off" can mean to deprive someone of an inheritance, but only in a money/family-legacy context (e.g., "cut off without a penny"); the sentence is about speaking, not money, so this sense does not apply.

• "Rebuked him" — this means to scold or criticise; the sentence describes the father stopping the speech, not telling the son off, so it does not match.

• "Isolated him" — to isolate is to separate someone socially or physically; nothing in the sentence suggests cutting the son off from contact with others.