Oracle America, Inc. v. Google Inc.
750 F.3d 1339 (Fed. Cir. 2014), cert. denied, 83 U.S.L.W. 3240 (U.S. June. 29, 2015) (No. 14-410)
API stands for "Application Programming Interface". It's a piece of code that allows two programs to communicate. These can be simple or elaborate, but all APIs are designed to allow third parties to read or send data. A robust discussion of API design has emerged, and today API design is an important part of business and even government.
The online tech community was happy with the district court opinion in this case, and mostly considers this opinion disastrous, although obviously Oracle is happy. The district court has yet to consider Google's Fair Use defense on remand.