What does "ungrammatical" mean?

In violation of one or more of the rules and conventions of a language as defined by the grammar, resulting in unacceptable or incorrect usage.

What is a synonym for "ungrammatical"?

Common synonyms include: barbarous, grammar free, ill-formed, improper, incorrect, poor diction.

adj

adj ·Rare ·Advanced level

Adjective

1
In violation of one or more of the rules and conventions of a language as defined by the grammar, resulting in unacceptable or incorrect usage.
"My Greek is not the tongue of Homer or Aeschylus but a sloppy ungrammatical sabir lacking Attic salt and tending to a saccharinity which sets my teeth on edge."

Adjective

1
not grammatical; not conforming to the rules of grammar or accepted usage wordnet

"These ungrammatical sentences resulted from the application of the additional rule F."

From un- + grammatical.