Wiktionary
n. (context grammar English) Noun case used to indicate location '''on''' an object. In English, it roughly corresponds to the prepositions "on" or "on top of," as in "on top of the house." Hungarian is a language that uses the superessive case.
Wikipedia
The superessive case ( abbreviated ) is a grammatical declension indicating location on top of, or on the surface of something. Its name comes from Latin supersum, superesse: to be over and above.
While most languages communicate this concept through the use of adpositions, there are some, such as Hungarian which make use of cases for this grammatical structure.
An example in Hungarian: a könyveken means "on the books", literally "the books-on".
In Finnish, superessive is a type of adverb. For example:
kaikkialla means "everywhere" (literally "everything-at")
täällä means "(at) here" (from tämä - "this", lit. "at this place")