involuntary muscle
nounUK /ɪnˈvɒləntəri ˈmʌsəl/
US /ɪnˈvɑːlənteri ˈmʌsəl/
A muscle that moves without you thinking about it.
Your heart is an involuntary muscle that keeps beating all day.
OTHER MEANINGS
2. Muscle tissue not under conscious control, such as the muscles of the stomach and intestines.
The walls of the intestines are made of involuntary muscle that pushes food along.
3. The muscle of the heart, which beats automatically without conscious effort.
Doctors studied the involuntary muscle of the heart to understand its rhythm.
4. Any muscle controlled by the autonomic nervous system rather than by will.
Blinking and breathing partly involve involuntary muscle activity.