As nouns the difference between pus and abscess

is that pus is a whitish-yellow or yellow substance composed primarily of dead white blood cells and dead pyogenic bacteria; normally found in regions of bacterial infection while abscess is a cavity caused by tissue destruction, usually because of infection, filled with pus and surrounded by inflamed tissue.

As an initialism PUS

is permanent Under Secretary (UK.

As a verb abscess is

to form a pus filled cavity typically from an infection.