The Collaborative International Dictionary
Grammaticaster
Grammaticaster \Gram*mat"icas"ter\, n. [LL.] A petty grammarian; a grammatical pedant or pretender.
My noble Neophite, my little grammaticaster.
--B.
Jonson.
Wiktionary
grammaticaster
n. (context derogatory English) A pedantic, inferior grammarian.