1. not conforming to the rules of grammar; violating standard grammatical conventions
Usage: commonly used in linguistics and language education

Examples

• The sentence 'He go to school' is nongrammatical because it lacks proper subject-verb agreement.
• Linguists often mark nongrammatical constructions with an asterisk in their analyses.
• Even though the phrase sounds natural in speech, it is technically nongrammatical.
• Students need to identify nongrammatical sentences and correct them.
• The nongrammatical use of 'whom' in casual speech is becoming more common.
• A nongrammatical sentence may still be understood by native speakers.