The general meaning of the term "appeal" is broader than the concept of Rechtmittel, which is more of an "appeal of a judicial decision".
There are multiple definitions - click on the translation that matches your context.
the action of asking a higher court to review and change the decision of a lower court; a review by a higher court of a decision made by a lower court
She lost both the case and the appeal. Her final route of appeal is before the Grand Chamber of the European Court.