Wiktionary
vb. 1 (context transitive English) To tune (an engine, industrial process, etc.) automatically. 2 (context music English) To correct the pitch of a vocal or instrumental performance.
Wikipedia
Auto-Tune is an audio processor created by Antares Audio Technologies which uses a proprietary device to measure and alter pitch in vocal and instrumental music recording and performances. It was originally intended to disguise or correct off-key inaccuracies, allowing vocal tracks to be perfectly tuned despite originally being slightly off-key.
The processor slightly shifts pitches to the nearest true semitone (to the exact pitch of the nearest tone in traditional equal temperament). Auto-Tune can also be used as an effect to distort the human voice when pitch is raised or lowered significantly, such that the voice is heard to leap from note to note stepwise, like a synthesizer.
Auto-Tune is available as a plug-in for professional audio multi-tracking suites used in a studio setting and as a stand-alone, rack-mounted unit for live performance processing. Auto-Tune has become standard equipment in professional recording studios. Instruments like the Peavey AT-200 guitar are seamlessly using the Auto Tune technology for real time pitch correction.
Auto-Tune was initially created by Andy Hildebrand, an engineer working for Exxon. Hildebrand developed methods for interpreting seismic data and subsequently realized that the technology could be used to detect, analyze, and modify the pitch in audio files.