“Cusp” translates as “cúspide” and “umbral”. The word comes from Latin (cuspis). To be on the “cusp of” doing something means that you are at a point of transition.
The word has other uses. A cusp is a fixed point on a mathematical curve. Dentists sometimes repair a broken cusp (una cúspide rota), and we have teeth with cusps, the grinding part of a tooth (to grind = rechinar).
The medical profession speaks of cusps, that is, a folds or flaps (colgajos) of a cardiac valve.
Here are some examples of everyday use of cusp:
- Great Britain is on the cusp of leaving the European Union (…está a punto de salir …).
- April marks the cusp of winter and spring (…marca el umbral de invierno a la primavera).
- Adrian´s dentist is going to repair the broken cusp (…va a arreglar la cúspide rota).
- Great Britain is on the cusp of a major breakthrough for a Covid cure (…está en la cúspide de un gran avance para una cura…).
So, are you on the cusp of doing something? Probably.