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A Grammar Hammer is someone who annoyingly interrupts what your saying to correct your grammar. He hammers you with his correct English per-say.
Teenager: Man this test is so much more hard then the last one!

English teacher comes up to teenager 1 and his friend.

English Teacher: No! What you should say is "This test is so much HARDER THAN the last one."
Teenager: God this guy is such a Grammar Hammer!
by Dr. M0 September 06, 2009
A popular club in many high schools around the North West of England where students can get help with any aspect of English that they are finding a problem.
Having a problem with English? Why not go to Grammar Hammer?
by Gemma Rowlands March 02, 2009