Not in accord with the rules of grammar.(adjective)
Not in accord with standard or socially prestigious linguistic usage.(adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "ungrammatical" in a sentence
"The fourth sentence should sound ungrammatical which is what the asterisk means."
"Coverdale's translation is not "ungrammatical" as far as the Hebrew language is concerned, notwithstanding that it was rejected in the reign of James I. ¤lechem¤, "bread," is evidently the accusative noun to the transitive verb ¤yiten¤, "He shall give.""
"What seems so horribly wrong about Palin's speech is that it borrows the strngth of demotic English, not to express thought forcefully - as ordinary, even "ungrammatical" English can do - but to cover for dishonesty and moral aridity."