latissimus dorsi

/L AH0 T IH1 S IH0 M AH0 S D AO0 R S IY0/
noun
  1. 1

    A large, flat, dorsolateral muscle on the trunk, posterior to the arm, and partly covered by the trapezius on its median dorsal region.

Source: https://en.wiktionary.org/wiki/latissimus%20dorsi