Someone perceived as being of little value or worth, as evidenced by being ignored when others are getting attention. Usually used as a semi-rhetorical question. Origin probably in American Jewish humor of the early-to-mid 20th century.
"What am I, chopped liver?" "What do I look like, chopped liver?"
(adjective) nobody, the person that the others ignore him and consider him nothing.
I feel chopped liver in dis fucking hood.