As a Verb or Adjective:
1. To start to do something after either hesitating or waiting for permission to do so, or even contrary to the wishes of others. English = go ahead, proceed.
2. To suggest someone do something or to challenge someone to do something to show how brave or reckless they are. English = dare.
1. Used alone to express angry disregard for others comments. English = 'I don't give a damn what you think!', 'I don't care (I'll do it anyway!'), 'So what! (I'll do it anyway!'), and so on.
2. Used alone to express anger or annoyance. English = 'Damn!', 'Damn it!', 'Blast!', and so on.