What does 회자 (膾炙) literally mean?

 ANSWER: raw meat [and] roasted meat

The word 회자 (膾炙) literally means "raw meat (膾) [and] roasted meat (炙)," which are so popular with Koreans that they always seem to be eating them. As a metaphor, 회자 is also used to refer to expressions or sayings that are popular with Koreans. My Korean-English dictionary defines 회자하다 as "become the talk of all," "be a household word," and "be well-known to everybody."

Here is a Korean sentence using 회자하다 that I came across this morning:

한동안 회자됐던 표현을 빌리자면 작품이 살아야 비평이 산다.

If I can borrow an expression that was popular for quite a while, "A [literary or artistic] work must exist for criticism to exist."

By the way, my Korean-English dictionary defines 인구 (人口) as "population," but 인구 literally means "a person's (人) mouth (口)" or "people's mouths," so even though 인구에 회자된 표현 can translate as "a popular expression or saying," it literally means "an expression that has become raw and roasted meat in people's mouths." 

From Dong-A's Prime Korean-English Dictionary

From Dong-A's Prime Korean-English Dictionary