1. A change to a product which is intended to make it better in some way, e.g. new functions, faster, or occasionally more compatible with other systems. Enhancements to hardware components, especially integrated circuits often mean they are smaller and less demanding of resources. Sadly, this is almost never true of software enhancements.
2. Marketroid-speak for a bug fix. This abuse of language is a popular and time-tested way to turn incompetence into increased revenue. A hacker being ironic would instead call the fix a feature, or perhaps save some effort by declaring "That's not a bug, that's a feature!".
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Nearby terms: Enhanced Integrated Drive Electronics « enhanced parallel port « Enhanced Small Disk Interface « enhancement » ENIAC » Enigma » ENOB