Amangala means “inauspicious” (See MANGALA). It is one of four crucial terms in Indian culture; the others are mangala (auspicious), SHUBHA (purity), and ashubha (impurity).
Further reading: John B. Carman and A. Marglin, eds., Purity and Auspiciousness in Indian Society (Leiden: E. J. Brill, 1985); B. Holland, compiler, Popular Hinduism and Hindu Mythology: An Annotated Bibliography (Westport, Conn.: Greenwood Press, 1963).
Encyclopedia of Hinduism. A. Jones and James D. Ryan. 2007.