Programmed Data Processor (PDP) was the name of a series of minicomputers made by Digital Equipment Corporation.
The PDP series started with the PDP-1, an 18-bit machine used in early time-sharing operating system work, and prominent in early hacker culture. One of the first computer games, Spacewar!, was developed for this machine.
The name "PDP" intentionally avoided the use of the term "computer" because, at the time of the first PDPs, computers had a reputation of being large, complicated, and expensive machines, and the venture capitalists behind Digital (especially Georges Doriot) would not support Digital's attempting to build a "computer"; the word "minicomputer" had not yet been coined. So instead, Digital used their existing line of logic modules to build a Programmable Data Processor and aimed it at a market which could not afford the larger computers.
Source: Wikipedia, "Programmed Data Processor", available under the CC-BY-SA License.