Adverbial phrase. Mid-17th century
[Latin, lit. 'to sickness', Cf, earlier USQUE AD NAUSEAM]
To a disgusting or tiresome extent.
This is probably my favourite Latin phrase because it's so easy to understand. If you're told that you're harping on about the rules of correct grammar ad nauseam, you know exactly what's being said, whether you're familiar with Latin phrases or not. It's also used in the phrase argumentum ad nauseam, when an argument is made so frequently or with such sickening repetition that everyone ceases to care in the end; completely and utterly sick of it.