Initialism of preferred gender pronoun.
"When filling out the form, please write your PGP next to your name so we can address you correctly."
In plain English: PGP is an encryption system that scrambles your messages so only you and the person you're talking to can read them.
"The email was encrypted with PGP to keep the personal details safe from hackers."
Initialism of Pretty Good Privacy. (A program using public key encryption popularly used with email.)
"She encrypted her sensitive documents using PGP to ensure they remained secure during transmission."