This is the 8272nd most frequent Russian word.
матеуша
The word "матеуша" does not have a known meaning in Russian; it may be a misspelling, a proper noun, or a non-standard term.
Here, "матеуша" is used as a term referring to a person's name in the context of actions they are performing.
Матёша готовится к важному экзамену в университете.
Mateusha is preparing for an important exam at the university.
In this sentence, "матеуша" is the name in oblique case showing the person that was met during a specific event.
Мы встретились с Матёшей вчера вечером на ужине.
We met with Mateusha yesterday evening at dinner.
This usage of "матеуша" refers to possession, indicating the book belonging to the person named Mateusha.