Lack of movement is a term used to describe a state of inactivity or stagnation. INACTION, with 8 letters, is defined as the failure to take action when it is needed. INERTIA, with 7 letters, is the resistance of any physical object to a change in its state of motion or rest. STILLNESS, with 9 letters, is the absence of any movement or activity. INERTNESS, also with 9 letters, is the quality of being inactive or sluggish. All of these terms can be used to describe a lack of movement.