akami
noun
aka·mi ä-ˈkä-mē 
: the lean, reddish flesh from along the spine of the tuna that is used especially for sushi and sashimi
When preparing this sushi at home, the choice of tuna is nearly always the akami, the nonfatty red meat, because of its availability and reasonable price.
Hiroko Shimbo, The Sushi Experience, 2006
Hiroko Shimbo, The Sushi Experience, 2006
Word History
Etymology
borrowed from Japanese, literally, "lean meat," from aka "red" + mi "body, flesh, meat"
First Known Use
1974, in the meaning defined above