While the purpose and effect of the Einstweilige Verfügung and a preliminary injunction are identical (preserve the status quo, before irreparable harm occurs, until a financial decision on the merits can be obtained), the scope and standards for issuing such relief are a bit different. To obtain a preliminary injunction in the US, a party must show that it will suffer irreparable harm unless the injunction is issued. When determining whether to grant preliminary injunctions, judges consider the extent of the irreparable harm, each party's likelihood of prevailing at trial, and any other public or private interests implicated by the injunction. The degree of irreparable harm and balancing of interests required to warrant the issuance of a preliminary injunction under German law is simply different than in the US.
There are multiple definitions - click on the translation that matches your context.
a court order made in the early stages of a lawsuit that prohibits the parties from carrying out a disputed act until the end of the trial
Ms Elliott's former employer sought a preliminary injunction in order to restrict her activities until the end of the lawsuit (=court case).