Real Dictionary

bug
A bug is an insect or similar small creature.
countable noun: A bug is a tiny hidden microphone which transmits what people are saying.
countable noun: A bug is an illness which is caused by small organisms such as bacteria.
countable noun: If there is a bug in a computer program, there is a mistake in it.
verb: If someone bugs a place, they hide tiny microphones in it which transmit what people are saying.

Bug in American English
river in S Ukraine, flowing southeastward into the Black Sea: 530 mi (853 km)

bug in American English 1
any of an order (Hemiptera) of insects with sucking mouthparts and with forewings thickened toward the base, as a water bug or squash bug
noun: a hemipterous insect

bug in American English 2
a bugbear; hobgoblin
noun: a bogy; hobgoblin

Bug in British English
noun: a river in E Europe, rising in W Ukraine and flowing southeast to the Dnieper estuary and the Black Sea. Length: 853 km (530 miles)

bug in British English 1
noun: any insect of the order Hemiptera, esp any of the suborder Heteroptera, having piercing and sucking mouthparts specialized as a beak (rostrum)
verb: to irritate; bother

bug in British English 2
noun: an evil spirit or spectre; hobgoblin

bug in British English 3
verb