A shacket is mixture of the word shirt and jacket. It is as shirt with long jacket sleeves, a hood, and fabric that has the thickness of a jacket. It doesn't have a zipper in which most jackets have that why shirt is part of the word.
The shacket was so named after a young, dynamic and trend setting law student, Alex Chelesnik when she purchased an oversized mens shirt and wore it as a jacket around NYC.