move a muscle

not move a muscle

1. To not move at all; to stay completely still. When I looked down and saw the snake, I didn't move a muscle until it slithered past me. Sit still until I come back, do you hear me? Don't move a muscle!
2. To not do anything, especially in a situation when one should help. You didn't even move a muscle when I came in with the groceries. A little help next time. The kids have been glued to the TV all day not moving a muscle.
See also: move, muscle, not
Farlex Dictionary of Idioms.

move a muscle

Bestir oneself even slightly. This idiom is usually put negatively, either with implied criticism, as in She won't move a muscle to help get dinner, or not, as in When I saw the deer, I stayed quite still, not daring to move a muscle. It was first recorded in 1889.
See also: move, muscle
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • not move a muscle
  • get by
  • on the move
  • move over
  • get a move on
  • move down
  • not move an inch
  • move away from (something)
  • move it
  • roll over
References in classic literature
I was now thoroughly awake, but as unable to move a muscle as though turned to stone.