bug
1. An insect, especially one of the order Hemiptera (true bugs). 2. Any of various species of marine or freshwater crustaceans. 3. Any insect, arachnid, or other terrestrial arthropod regarded as a pest. 4. In computing, an error or defect in software or hardware causing malfunction or unexpected behavior.
Etymology
Origin: Old English
Root: bugge (scarecrow, hobgoblin) — "cow, ox"
Example
"The software developer spent hours tracking down a persistent bug that caused the application to crash unexpectedly."
Usage Notes
Bug has dual meanings: biological-referring to true bugs (Hemiptera) or any pest, and technical-referring to software errors. The computing sense was used in the 19th century, predating the famous moth-in-computer anecdote. Informal register in both contexts. Common error: assuming all insects are 'bugs' - technically only Hemiptera qualify, though casual usage includes any small pest. 'Bug' is also colloquially used for minor illnesses ('stomach bug').