ungrammatical

un- +‎ grammatical

ungrammatical (comparative more ungrammatical, superlative most ungrammatical)

1. (linguistics) 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.

In formal linguistics, ungrammatical sentences are labelled using an asterisk (*):

*The subject of this sentence is.

This convention goes back at least as far as Leonard Bloomfield's Language (1933).

• agrammatical
• ungrammatic

• grammatical

• ungrammaticalized