English Reference
noun · verb

bug

n. · v.
US /ˈbəɡ/ UK /bˈʌɡ/ bug UK spelling bug's, bug's

  1. 01 A2 Elementary Informal

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

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

    Simple

    We couldn't eat outside because there were too many bugs flying around the food.

    In context

    The biologist noted that while the children called every crawling creature a bug, only a few belonged to the order Hemiptera.

  2. 02 B1 Intermediate Informal Medicine

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

    n.a non-specific contagious illness or the microorganism that causes it.

    Simple

    I missed work yesterday because I picked up a stomach bug from my toddler.

    In context

    Public health officials warned that a particularly resilient flu bug was circulating through the primary schools this winter.

  3. 03 B2 Upper Intermediate

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

    n.a concealed electronic eavesdropping or intercept device used for surveillance.

    Simple

    The detectives found a bug hidden behind the picture frame in the suspect's office.

    In context

    Intelligence officers suspected the embassy had been compromised and conducted a sweep to locate any hidden bugs.

    microphonewiretap
  4. 04 C1 Advanced Informal

    n.a sudden strong interest in a new hobby or activity.

    n.a sudden enthusiasm or obsession for a particular activity or subject.

    Simple

    After his first trip to the mountains, he really caught the hiking bug.

    In context

    She had never cared for gardening until last spring, when she suddenly caught the bug and transformed her entire backyard.

  5. 05 B1 Intermediate Informal

    v.to bother or annoy someone.

    v.to cause persistent annoyance or irritation to someone.

    Simple

    It really bugs me when people talk loudly on their phones in the library.

    In context

    The constant flickering of the overhead light began to bug the office staff, affecting their concentration throughout the afternoon.

    annoybotherpester
  6. 06 B2 Upper Intermediate

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

    v.to equip a room, building, or communication device with a concealed listening apparatus.

    Simple

    The police had to get a warrant before they could bug the criminal's house.

    In context

    The thriller depicts a rogue agent who manages to bug the boardroom just minutes before the high-stakes meeting begins.

    wiretapmonitor
  7. 07 C2 Proficiency Informal

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

    v.to protrude or bulge, typically in reference to the eyes due to shock or medical conditions.

    Simple

    His eyes bugged out when he saw the massive bill for the car repairs.

    In context

    The witness's eyes bugged in disbelief as the defendant suddenly stood up and confessed to the crime in open court.

    bulgeprotrude

Health experts still need to confirm that eggs are the source and the UKHSA is continuing to interview people confirmed to have caught the bug.

BBC News· 19 Aug 2026

From the Slavic hydronym bugъ /buga.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Level B2 · Upper Intermediate
Frequency Common
Updated