Definition of "prescriptivist"

The plutocratic tone and styptic wit of Safire and Newman and the best of the Prescriptivists is often modeled after the mandarin-Brit personas of Eric Partridge and H. W. Fowler, the same Twin Towers of scholarly Prescriptivism whom Garner talks about revering as a kid.

2001 April, David Foster Wallace, “Tense Present: Democracy, English, and the Wars over Usage”, in Harper's Magazine

In short, they tend to present Indian English as nothing more than "standard" English with a select collection of lexical peculiarities tacked on, as it were, many of which would be regarded as "errors" by prescriptivist language scholars.

2012, James Lambert, “Beyond Hobson-Jobson: A new lexicography for Indian English”, in World Englishes‎, page 312