Name for a verb that switches meaning depending on whether it has an object

Consider the sentences:

The door closes.

Emily closes the door.

In both cases, it's the door that's being closed, even though "the door" is the subject of the first sentence and the object of the second.

Some verbs, like "close", behave like this and switch their meaning according to whether they're used intransitively or transitively. Another good example might be "fly". A few years ago, I was told a name for this type of verb, but I can't for the life of me remember it now. What are these verbs called?

Solution 1:

I’m not aware of a single term that describes exactly verbs that display this type of alternation between intransitive subject and transitive direct object, but it is a common feature of many unaccusative verbs in English (in particular anticausative verbs, and if you used unaccusative verb as a term to refer to this ‘group’ of verbs, you would likely be understood.

In general, a closer unity between the subject of an intransitive verb and the direct object of a transitive verb is a typical feature of ergativity, probably the most common ergative feature to show up in non-ergative languages (like English). In ergative languages, however, this relationship is the norm and is usually displayed by all verbs.

In English, the difference between an unaccusative verb and an ergative verb is the verb’s valency: unaccusative verbs are intransitive, while ergative verbs by definition are transitive. Close, for example, is both an unaccusative and an ergative verb: in your first example it is unaccusative (the subject is non-volitional and not actively responsible for the action), while in your second example it is ergative (a regular transitive verb with a volitional subject and non-volition object, but one that corresponds to an unaccusative intransitive).

(Some people—and the Wikipedia article on ergative verbs—categorise unaccusatives as a subcategory of ergative verbs; there’s nothing particularly wrong with this, except it leaves you without a word specifically for the transitive half of an unaccusative–ergative pair.)

Solution 2:

Janus Bahs Jacquet's answer put me on the right track, and I was able to find the answer I was thinking of:

In linguistics, an ergative verb is a verb that can be either transitive or intransitive, and whose subject when intransitive corresponds to its direct object when transitive.

http://en.wikipedia.org/wiki/Ergative_verb