| Definition -
An ambitransitive verb that when used in its transitive form can take a direct object that is semantically equivalent to the verb's subject when the verb is used in its intransitive form.
(1) The window broke (intransitive, window is the subject)
(2) I broke the window. (transitive, window is direct object).
In the above, in both cases the word window is semantically equivalent whether it is used as a subject or an object. This means that the verb break is an ergative verb.
In contrast, the verb paint is not an ergative verb, because saying Dave paints is very different from saying Dave was painted.
Etymology - The term derives from the Greek ergon, work.