mainmuscle
nounUK /ˈmeɪnˌmʌsəl/
US /ˈmeɪnˌmʌsəl/
The mainmuscle is the biggest, strongest muscle that does most of the work.
Your heart is the mainmuscle that pumps blood all day.
OTHER MEANINGS
2. The most important muscle used for a certain action.
For chewing, the jaw's mainmuscle does most of the biting.
3. The muscle a person relies on most when lifting.
He trained his mainmuscle group before the big race.
4. The central muscle in a group that supports the others.
The mainmuscle of the back keeps you standing straight.