Many North American and Siberian languages allow the direct object of a verb to be incorporated into the verb itself. It is pronounced as part of the verb, and may have verbal affixes attached to it. It is in some ways like a compound word, but any noun of the appropriate type may be (or in some cases must be) incorporated.

Normally the object is less specific when incorporated. You don't get free variation between two clauses, both meaning the same thing, one with incorporation and one without: the process has the effect of reducing the salience of the object. This is mirrored in English translation by omitting determiners like 'the, a, some'.

In this Nahuatl (Aztec) example, the word nacatl 'flesh' loses its absolute ending and is reduced to a stem, which is inserted between the subject prefix and the verb, replacing the object prefix -c-:

ni-c-qua in  naca-tl
I-it-eat the flesh-ABS
'I eat the flesh'

'I eat flesh'

In many incorporating languages it also turns a transitive verb into an intransitive one. In Chukchee (Siberia) the transitive subject goes in the ergative case, and the object goes in the absolutive, as does an intransitive subject. The verb also marks the subject/object relation. When the object is incorporated into the verb, the remaining subject is now marked with the absolutive, and the verb is marked for a subject only. (The verb and object also change phonetic form.)

ətləg-e    qorangə       təm-nen
father-ERG reindeer(ABS) kill-PAST:he/it
'Father killed the reindeer'

ətləg-ən   qaa-nmə-g?e
father-ABS reindeer-kill-PAST:he
'Father killed a reindeer'
In effect they are creating verbs 'to flesh-eat', 'to reindeer-kill', meaning to eat flesh generally, to do some killing of reindeer. While it is usually the direct object that is incorporated, it can be other actants such as instruments, or the subjects of stative or unaccusative verbs, those that don't actively do anything. In Huahtla Nahuatl ya' kikochillotete'ki panci 'he knife-cut the bread' incorporates kochillo 'knife', while in Onondaga kahsahe?tahíhwi is a verb meaning 'it beans-spilled' or 'there was beans-spilling'.

You never get active subjects incorporating, to give verbs like 'to father-kill', taking a separate object. The closest you can get is when the relationship is reversed, effectively incorporating the agent from the passive voice. So in Southern Tiwa khwienide kanêdeureban 'the dog was horse-kicked'. But no language uses an incorporation like *'horse-kicked the dog'.

Outside the various Siberian and American language families that use it true incorporation is very rare: some non-Pama-Nyungan languages of northern Australia also do it. But a lot of languages have strategies that are similar. In Japanese foreign words are made verbs by placing them next to suru 'to do': so 'to study' is benkyoo suru. However, the noun can also take the accusative particle o like a normal object. There is also no phonetic fusion in these newly-created words, though older ones do exist with the suru changed to a suffix -zuru or -ziru.

English can freely make lexical compounds of noun and verb, with the result being another verb. Examples are: to colour-code, to baby-sit, to window-shop, to carbon-date, and to breast-feed. However, all of these have special meanings: none is simply the incorporation of the direct object. To window-shop isn't to shop a window, and to breast-feed isn't to feed a breast. Typically they are incorporations of prepositional phrases, and it is not strictly predictable which: to code with colours, to shop in windows, to feed from breasts.

English can't form compound verbs of the incorporating type, like *flesh-eat or *car-drive or *deer-hunt. (Nor can it incorporate subjects, like *father-kill or *horse-kick, but no language can.) Strikingly though, it very freely allows these compound verbs inside larger compounds formed by affixation; you can't car-drive to work, and you can't car-drive a Mercedes, but you can be a car-driver and go in for car-driving. These are transparent in meaning: a car-driver is just a driver of a car, and deer-hunting is just the hunting of deer. One theoretical reason that the verbs like *deer-hunt are not found may be that this morphology is in direct competition with the syntax 'hunt deer', combining the same elements and with the same meaning. If either different structural trees are combined, or the resultant structure has a distinct idiomatic meaning, the morphological compounding is allowed. (Actually, a Web search does show quite a few hits for a verb 'deer-hunt', so the principle isn't watertight; they seldom are.)

In incorporating languages proper, some use the incorporated head noun as a classifier. In these languages, 'to car-drive' remains transitive, continuing to allow an object, and you can car-drive a Mercedes. But in others, 'to car-drive' has used up the verb's object slot.

Gerdts, D. 'Incorporation', in Spencer and Zwicky (eds), 1998, The Handbook of Morphology, Blackwell