How can i make App.api.call() synchronous and asynchronous?

How can i make App.api.call() synchronous and asynchronous?

Is there any flag available which can handle the call?

Currently i have exposed one custom end point and calling the same from client (Account Save Button). I want to wait at client side (Inside Save Override function ) unless i get the response from Custom End point.

How can i do this?

Regards,
Deepak