adj

• (grammar) With the subject of a transitive construction having grammatical cases or thematic relations different from those of an intransitive construction.
  "The case systems of ergative languages are counter-intuitive to speakers of Indo-European languages."

noun

• (grammar) Ellipsis of ergative case (“a grammatical case used to indicate the agent of a transitive verb in ergative-absolutive languages”).
  "Samoan, for example, differs from the usual pattern displayed by split ergative languages in that the appearance of the ergative is grounded in sociolinguistic factors as well as syntactic ones. The more formal register of Samoan requires the ergative on all postverbal transitive subjects. The less formal register allows the ergative not to be expressed at all."
• (grammar) An ergative verb or other expression.
  "Unlike those with subjectivized ergatives, such locative clauses naturally do not allow for imperatives (*Contain the apples)."