This is actually a lowlands Scottish term to walk to the left or counter-clockwise within a compass round.

The actual direction you move is not important to spirits or to energy, but traditionally most Trads walk widdershins when they wish to dissipate energy, during the closing of a compass, and during such rites as the purification of a house.

A few Trads do the opposit.  You should follow your tradition. If you have no specific tradition, use the more popular counter-clockwise direction.

The opposite of widdershins is deosil.

In the Southern Hemisphere (Australia, South Africa, New Zealand) the opposite to the above information is true. But consult with a local Crafter or a Crafter in your countryto be sure.