Bugs are usually thought of as insects, but not all insects are bugs. True bugs belong to a separate order called Hemiptera and have piercing and sucking mouthparts. Despite this, bug continues to be a colloquial, blanket term for bothersome insects that require some sort of pest control.
The term “bug” also commonly applies to a glitch or problem in computer software or programming. If a new program or system has been installs and users experience problems, it is send to have “a few bugs” in it. For example, Apple’s new operating system Mountain Lion has a few bugs in battery life for some users.
Some other uses for the word “bug” include a craze or obsession (bitten by the acting bug) or a secret listening device, and even to pester someone.