Avaihh lli vastam was a term in Old High Rihannsu which translated into "warp 7 capable stardrive" which was a project made by the Romulan Star Empire in the 22nd century. The purpose of the project was to provide the Romulan people an advantage over the other neighboring powers which included the Coalition of Planets.
The project was overseen by Doctor Ehrehin in 2154 and was revolutionary as it would have involved the use of quantum singularity-based power systems. Unfortunately, the project would be stalled and never see completion at the time. (ENT novel: The Good That Men Do)