ungrammatical

It is ungrammatical to end a sentence with a preposition.

The ungrammatical use of slang can make your writing sound unprofessional.

She made an ungrammatical mistake in her essay.

It's ungrammatical to use a singular verb with a plural subject.

The teacher pointed out the ungrammatical phrases in the student's composition.

He often makes ungrammatical errors when speaking English.

The ungrammatical sentence confused the readers.

You should avoid using ungrammatical expressions in formal writing.

The ungrammatical structure of the sentence made it difficult to understand.

She corrected the ungrammatical sentence before submitting her paper.