Grass sb up Meaning / Examples / How to Use

What Does “Grass sb up” Mean?

“Grass sb up” is a British informal phrasal verb meaning to inform on someone, usually to the police or an authority, often betraying their trust.

Introduction

The phrase “grass sb up” is commonly used in British English to describe the act of telling someone in authority about another person’s wrongdoing. It usually implies a sense of betrayal or informing on someone, especially in situations involving rules or laws. Understanding the “grass sb up meaning” helps learners recognize when someone is being reported or “snitched” on. This phrase is often heard in conversations about crime, school, or work environments where trust is important. Knowing how to use “grass sb up” correctly will help you sound more natural in informal conversations and understand British slang better.

Quick Info Box

• Phrasal verb: grass somebody up
• Type: transitive
• Level: B2 (Upper-Intermediate)
• Short meaning: to tell the authorities about someone’s bad behavior

Structure (Grammar Rules)

“Grass sb up” is a transitive phrasal verb and is separable. You can place the object (somebody) between “grass” and “up” or after the whole phrase.

Examples of structure:

• grass + somebody + up (separable): He grassed me up to the teacher.
• grass + up + somebody (less common): He grassed up me. (less natural)
• grass + somebody up (inseparable): He grassed me up.

How to Use “Grass sb up”?

You use “grass sb up” when talking about someone telling an authority figure about another person’s wrongdoing. It is informal and often negative because it implies betrayal. It is mostly used in British English and often in contexts involving rules, crime, or school situations.

It is usually directed at the person who is being reported (the object) and the person who is telling (the subject).

Examples

Imagine a student telling on a classmate who cheated on a test. You could say:

• “He grassed me up to the teacher because I didn’t do my homework.”
• “Don’t grass me up or I’ll be in trouble.”
• “She grassed him up for stealing from the shop.”
• “I’d never grass my friends up to the police.”
• “If you grass me up, you’ll lose my trust.”

Here’s “grass sb up in a sentence” showing its common use: “Tom grassed his brother up after finding out he broke the window.”

Common Mistakes

Sometimes learners confuse “grass sb up” with other reporting verbs or make grammar errors. Here are some examples:

• Incorrect: He grass up me to the police.
• Correct: He grassed me up to the police.
• Incorrect: She grassed on me about the mistake. (Different phrase, different meaning)
• Correct: She grassed me up to the teacher.

Remember, the correct phrase is “grass sb up,” not “grass on sb,” which is less common and slightly different in meaning.

Differences / Synonyms

“Grass sb up” is similar to “snitch on sb,” “tell on sb,” or “rat sb out,” but it is specifically British and more informal. Unlike “tell on,” which can be used by children, “grass up” often carries a stronger sense of betrayal.

• Snitch on: Used mainly in American English, informal, and means the same as “grass up.”
• Tell on: More general, can be used by children, less harsh.
• Rat sb out: Very informal and negative, implies betrayal like “grass sb up.”

Choose the phrase based on the tone and region.

Common Collocations

Common objects used with “grass sb up” include people and authority figures. Here are typical collocations:

• Grass sb up to the police: Reporting a crime
• Grass sb up to the teacher: Reporting bad behavior at school
• Grass sb up to the boss: Reporting misconduct at work
• Grass sb up for stealing: Reporting theft
• Grass sb up for cheating: Reporting dishonesty

Related Phrasal Verbs

Here are related phrasal verbs of grass sb up:

• Grass Sth Over

Real-life Dialogue

Here is a short conversation using “grass sb up”:

Anna: Did you hear what Jake did?

Ben: Yeah, I heard he grassed Sam up to the teacher for copying homework.

Anna: That’s so unfair. I wouldn’t grass my friends up like that.

Ben: Me neither. It’s better to talk to them first.

Practice

Fill in the blank with the correct form of “grass sb up”:

• If you _______ me _______ to the manager, I might get fired.
• Don’t _______ your classmates _______ for being late.
• She _______ him _______ after seeing him break the rules.

Answers:

• grass me up
• grass up
• grassed up

FAQs

• What does “grass sb up” mean? It means to tell someone in authority about another person’s wrongdoing.
• Is “grass sb up” formal? No, it is an informal British phrase.
• Can I use “grass sb up” in American English? It is understood but less common. Americans usually say “snitch on.”
• Is “grass sb up” negative? Yes, it often implies betrayal or disloyalty.
• Can I say “grass on sb”? “Grass on” exists but is less common and slightly different in meaning.