I have seen sometimes the concept of "offline authentication" in slides but I have never been able to map it to specific feature.
Now in Worklight 6.1 I see it in a table of features and the support for each platform:
http://www-01.ibm.com/support/docview.wss?uid=swg27039422
What is offline authentication and how does Worklight implements it? I understand it is not the same as "working offline".
Looks like "Offline authentication" is a reference to Encrypted Offline Cache... and the same can be achieved with JSONStore as well.
Source: Enhancing Your Mobile Enterprise Security with IBM Worklight
Theoretically you could devise an authentication flow that uses local secure storage for authentication needs.... I don't know how popular that would be...