Bug

Bug can mean many different things:

Biology
True bug, a group of insects
Bug, a slang word for a pathogen that makes organisms ill
Bug, a slang word for an insect, such as an ant or a beetle

Technology
Software bug, a problem with the code in a computer program
Bug, a device for telephone tapping
Bug, a nickname for a Volkswagen Beetle because of its shape

Other
Western Bug and Southern Bug, two rivers in Poland and Ukraine
Something that irritates somebody, such as "My loud neighbour really bugs me!"