# bug

/ˈbəɡ/ (US) · /bˈʌɡ/ (UK)

Source: https://englishreference.com/word/bug
Updated: 2026-08-15

## Senses

### 1. an insect

noun · CEFR A2 · Informal

a small insect or similar creature, especially one that people think is a pest.

For teachers: any small terrestrial invertebrate, particularly those perceived as pests; technically refers to the order Hemiptera but used broadly in general speech.

- We couldn't eat outside because there were too many bugs flying around the food.
- The biologist noted that while the children called every crawling creature a bug, only a few belonged to the order Hemiptera.

### 3. minor illness

noun · CEFR B1 · Informal

a small illness that spreads easily, like a cold or a stomach ache.

For teachers: a non-specific contagious illness or the microorganism that causes it.

- I missed work yesterday because I picked up a stomach bug from my toddler.
- Public health officials warned that a particularly resilient flu bug was circulating through the primary schools this winter.

### 4. listening device

noun · CEFR B2

a tiny hidden microphone used to secretly listen to what people are saying.

For teachers: a concealed electronic eavesdropping or intercept device used for surveillance.

- The detectives found a bug hidden behind the picture frame in the suspect's office.
- Intelligence officers suspected the embassy had been compromised and conducted a sweep to locate any hidden bugs.

### 5. enthusiasm

noun · CEFR C1 · Informal

a sudden strong interest in a new hobby or activity.

For teachers: a sudden enthusiasm or obsession for a particular activity or subject.

- After his first trip to the mountains, he really caught the hiking bug.
- She had never cared for gardening until last spring, when she suddenly caught the bug and transformed her entire backyard.

### 6. to annoy

verb · CEFR B1 · Informal

to bother or annoy someone.

For teachers: to cause persistent annoyance or irritation to someone.

- It really bugs me when people talk loudly on their phones in the library.
- The constant flickering of the overhead light began to bug the office staff, affecting their concentration throughout the afternoon.

### 7. to install surveillance

verb · CEFR B2

to hide a tiny microphone in a room or on a phone to listen to private conversations.

For teachers: to equip a room, building, or communication device with a concealed listening apparatus.

- The police had to get a warrant before they could bug the criminal's house.
- The thriller depicts a rogue agent who manages to bug the boardroom just minutes before the high-stakes meeting begins.

### 8. eyes bulging

verb · CEFR C2 · Informal

when your eyes open very wide because you are surprised or shocked.

For teachers: to protrude or bulge, typically in reference to the eyes due to shock or medical conditions.

- His eyes bugged out when he saw the massive bill for the car repairs.
- The witness's eyes bugged in disbelief as the defendant suddenly stood up and confessed to the crime in open court.

## Examples

- The software update fixed a major bug in the system.
- I missed the meeting because I caught a stomach bug that has been going around the office.
- While the hardware performed flawlessly during the initial stress tests, a subtle logic bug in the firmware caused the entire system to crash under heavy loads.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.