Which term specifies a condition that is stationary or not moving?

The term that specifies a condition that is stationary or not moving is "motionless." This word directly describes a state in which there is complete absence of movement. In various contexts, being motionless can refer to an object, a person, or a situation where no change or activity is occurring.

The other terms, while they may imply a lack of movement or change in some contexts, do not specifically convey the idea of being entirely stationary. "Progressive" often refers to something that is advancing or developing, which contradicts the notion of being stationary. "Variable" suggests changeability or the potential for change, indicating that something can move or alter. "Stagnant" typically refers to something that is not advancing or improving, like stagnant water, but it can carry connotations of an underlying lack of activity rather than an outright absence of movement. Hence, "motionless" is the most precise term for describing a condition that is not moving.