from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Not in accord with the rules of grammar.
- adj. Not in accord with standard or socially prestigious linguistic usage.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. In violation of one or more of the rules and conventions of a language as defined by the grammar, resulting in unacceptable, or incorrect usage.
from The Century Dictionary and Cyclopedia
- Not according to the established rules of grammar.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. not grammatical; not conforming to the rules of grammar or accepted usage
un- + grammatical (Wiktionary)