The phrase "incorrect grammar" means using words or sentence structures that are not considered correct according to the accepted rules and guidelines of a language.
Sentences with «incorrect grammar»
Nonetheless, they may use incorrect grammar or verb tense. (spellingcity.com)
Do you have a lot of incorrect grammar and spelling? (singleroots.com)
Despite incorrect grammar here and there, the message about the lesson remains clear. (californianstogether.org)