What is Willem C. Vis Moot?

Legal Definition
The Willem C. Vis International Commercial Arbitration Moot is an international moot court competition. Since 1994, it has been held annually in Vienna, Austria attracting more than 300 law schools from all around the world and spurring the creation of more than twenty pre-moots each year before the actual rounds are held in Vienna.

The object of the Vis Arbitral Moot is to foster study in the areas of international commercial and arbitration laws and encourage the resolution of business disputes by arbitration. The problem for the moot is always based on an international sales transaction subjected to the United Nations Convention on Contracts for the International Sale of Goods, 1980 (also referred to as the United Nations or the Vienna Sales Convention, or CISG) and also involves procedural issues of arbitration. The moot consists of submitting written memoranda prior to the moot on designated dates for both sides of the dispute (Claimant and Respondent in legal terminology). The oral arguments phase of the moot is held in Vienna.
-- Wikipedia