This word is acceptable for play in the UK dictionary that is being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

n. Someone who lays down rules regarding language usage, or who believes that traditional norms of language usage should be upheld.

adj. Having a tendency to prescribe.

n. A person who believes that acceptable practices should be prescribed by an authority rather than be determined by the usage of the general public; especially, a supporter of prescriptive{2} rules of grammar; -- also used attributively, as prescriptivist grammar.

"This isn’t out of the ordinary for prescriptivists; hardly a month goes by without the Language Loggers pillorying some foolishly certain prescriptivist for breaking the very rule the prescriptivist was trying to impose."

descriptivist   

prescriptivism    prescribe