Adharma, like dharma, is associated with one’s ashrama (stage of life) and varna (social status). Loosely, Adharma in Hinduism can be defined as unrighteousness. It is indefinable as the term dharma (which stands for individual values and social ideals).
Dharma is an ethico-social concept, a product of society and social institutions. Dharma and Adharma are like punya and papa, merit and wrong acts, terms referring respectively to what is good and what is bad for others. The concepts of dharma and adharma depend on tradition and custom. Even among the eternally valid values like truth and non-violence, it is difficult to come to any conclusion in a dilemma when they are mutually conflicting.
Telling a lie is not adharma if it is done to save a pious and innocent man.