Widdershins mean movement in a contrary or counterclockwise direction: taking course opposite to the motion of the Sun (in the Northern Hemisphere), going left wise, or keeping to the left. In some religions it is superstitiously considered as unlucky or evil. Etymology: wider,back + sinnes, in the direction of
In German language it is considered widersinnig, i.e., "against" + "sense".

However in magickal purposes, when a circle is casted deosil (clockwise) it is closed widdershins (anti-clockwise). It can be used to rid a circle or a person from negative energies. In some practices, it also used to raise negative spirits or energies however, it depends from practitioner to practitioner, faith to faith. Widdershins can be used both for positive
However the Law of Accountability is always prevalent in these cases. Each one of us is accountable for whatever we choose to do and think. There are always consequences to the actions we take and what we give we get back. So if we use Chaos magick or any magick in widdershins movement when it is not subscribed, just to take revenge, make the first strike or some other negative action, then we’re bound to receive the fruits for it. Apart from that, Widdershins is commonly used in rituals for positive purposes only. It is a prominent part of Wiccan rituals as when you cast a circle deosil it is important to close it
People relied on it for more than just light, and it played a role for ensuring survival through growing crops and cultivating bountiful harvests. Anything that moved against the Sun was thus viewed as negative, unlucky or evil. Further superstitions arose through folk myths and Celtic legends that spoke of Gods, Goddesses and heroes forcing people or things to move counter to the Sun in order to bring about chaos and turmoil. These are the reasons why misconceptions on Widdershins being a negative practice is still believed in.
* People believe any type of magick using Widdershin/ clockwise is evil though it is simply our intention and way one uses this magick, rather than the magick itself which is more accountable for the effect you are creating. People automatically believe that anything clockwise is negative however in some processes (though only after careful examination), anti clockwise is not only helpful but is necessary too.
* Because the sun played a very important role in quite a lot of older religions, thus to go against the sun was considered bad luck for sun-worshiping