Ungrammatical (adjective)

Not following the rules of grammar.

Origin:

Late middle english (in the sense "ignorant of grammar"): from un-1 + grammatical.

Examples:

1. His speech was full of ungrammatical sentences.
2. The teacher marked the essay as ungrammatical.
3. The ungrammatical construction made the sentence unclear.
4. Ungrammatical language in the report made it difficult to understand.
5. Her ungrammatical use of words detracts from the professionalism of her presentation.