Direct Action has been succinctly defined as any action where individuals or groups act directly themselves to try to bring about change rather than asking or expecting others to act on their behalf
- Howard Clark Preparing for Non violent Direct Action 1984

Direct action does not necessarily mean breaking the law e.g. boycotts, but some even though non violent, such as tax refusal or occupation etc, may involve a breach of the law.

Overlapping with some forms of direct action is civil disobedience - an open public defiance of the law aimed at bringing about change - for example Gandhi's campaigns to end British rule in India

Is non violent direct action really 'opting out' of a constitutional democracy?

It surely doesn't necessarily make one a 'criminal terrorist' !
(I don't think your argument about protesting in order to influence the government is helped atall by this level of hyperbole 'Willie')

It seems unlikely that, unlike the elected left wing government of Guyana overthrown by a CIA financed and organized strike in 1963, the overthrow of a well established British democracy - however imperfect - is in any real danger
I share the perceived concern of others however that, however well justified by circumstances, 'traditional liberties' like the right to strike, even to assemble may be curtailed little by little

It is important to remember that, in their day, Martin Luther King and civil rights activists were charged with being 'undemocratic' when they resorted to direct action and civil disobedience

Michael Randle* argues that only rarely can a democratically elected government be coerced even by a mass direct action campaign into changing a policy it is committed to as the reality is that they have the edge in purely physical force
But numbers can be important because they attract more media coverage and can work at a political as well as a symbolic level

* Direct Action a threat to democracy ? University of Bradford Dept of Peace Studies

Randle concludes that
"In any rate the proposition that civil disobedience should be altogether eschewed in a constitutional democracy carries its own, far greater, danger…
It chiefly operates within the democratic system through the power of drama and symbolism THROUGH APPEALS TO SHARED VALUES WITHIN THE SOCIETY AND THROUGH FACING THE AUTHORITIES WITH MORAL AND POLITICAL DILEMMAS IN DECIDING HOW TO PRECEED'