Corpus juris is a Latin term that means "body of law." It is a compendium of all cases, law, and the different explanations of these laws and cases. It can refer to any volume encompassing several collections of law.
There are many legal volumes that fit this definition. The most common however is Corpus Juris Secundum, an encyclopedia of the U.S. federal and state laws. Many states also have such books which contain a detailed explanation of state laws.