noun

• (medicine) Initialism of pelvic inflammatory disease. [(pathology) The infection of the upper part of the female reproductive system (uterus, fallopian tubes, and ovaries) and inside of the pelvis.]
• Initialism of personal identification device.
• (algebra) Initialism of principal ideal domain. [(algebra) An integral domain in which every ideal is a principal ideal.]
• (computing) Initialism of process identifier.
• Initialism of proportional integral derivative.
• Initialism of piping and instrumentation diagram.
• Initialism of photoionization detector.