Green’s Dictionary of Slang

piece of shit n.

also piece of crap
[fig. use of shit n. (1a)/crap n.1 (2)]

1. [1940s+] (orig. US) an unpleasant or disliked person.

2. [1940s+] (orig. US) anything unpleasant, disgusting or of poor quality, e.g. a piece of gross hypocrisy etc.