Formally, an insect of the order Hemiptera, also known as the "true bugs". (Outdated taxonomies sometimes use the name Heteroptera.)

Integrated circuit chip, for its buglike appearance

Volkswagen Beetle (slang)

Informally, a pathogen such as virus or bacteria that causes illness

Software bug, or software defect

Bug (2007 film), psychological thriller directed by William Friedkin

Device for telephone tapping

Bug (Starship Troopers), a fictional alien race from the novel and film Starship Troopers

Covert listening device

Web bug, an object that is embedded in a web page or e-mail that allows checking that a user has viewed the page or e-mail

Bug, a character in the Marvel comic book series The Micronauts

A semi-automated telegraph key

bug, ISO 639 code for the Buginese language

Bug (play), thriller/black comedy

Manually positioned marker in flight instruments

"Bug," a song by Phish from their 2000 album Farmhouse

Bug (2007 soundtrack), soundtrack of the film Bug (2007)

Bug! and Bug Too! video games

Western Bug, a river in Ukraine, Poland, and Belarus

A card cheat's bug is a holdout device

Bug (poker), a restricted wild card

Southern Bug, a river in Ukraine

Bug (1975 film), a film directed by Jeannot Szwarc in 1975

Bug (Dinosaur Jr. album), a 1988 album by Dinosaur Jr

Bug (2002 film), (2002) comedy-drama about a chain of events begun by a boy squashing a bug

Bug (Dave Davies album), a 2002 album by Dave Davies

Bicycle User Group

BUG Magazine, Croatian magazine

More colloquially, any arthropod (excepting most crustaceans); includes insects, but also non-insects such as spiders and centipedes.

A hybrid of a Pug and a Boston Terrier

A North American term for a digital on-screen graphic, generally used as a form of television station identification