As a Verb or Adjective:
1. To know what someone has signed and to understand what they mean by it. English = catch (someone's meaning), follow (someone's meaning).
Interactive:
1. Used alone with a positive facial expression to mean you did follow and understand what someone has just signed. English = 'Yes, I got that!', 'Yes, I'm following you.', and so on.
2. Used alone with a negative facial expression to mean you did not follow what someone has just signed. English = 'Sorry, I don't follow you.', 'I don't get it!', 'I didn't catch that!', and so on.