[Petronski]

The definition provided by Spotlight is faulty, as I already pointed out.

[antiRepublicrat]

The definition provided by Spotlight is faulty, as I already pointed out.

Then your problem is with the New Oxford American Dictionary.

[Swordmaker]

The definition provided by Spotlight is faulty, as I already pointed out.

The Spotlight definition is the definition of ad Hominem in the complete New Oxford American Dictionary.

Spotlight also provides free instant access to the New Oxford Writer's Thesaurus, and Wikipedia as well as Apple's on line support resources.

Here is a screen grab of the same results with the "All" option selected in the Spotlight dictionary:

Your claim of Spotlight being faulty is erroneous.