Stable atmosphere describes an atmospheric condition in which vertical movement within the atmosphere is suppressed due to atmospheric stability. In these conditions, the temperature of a parcel of air becomes cooler that its surrounds as it rises, resulting in it falling back down to the surface.
Source: Hardy, Colin C., Ottmar, Roger D., Peterson, Janice L., Core, John E., and Seamon, Paula. 2001. Smoke Management Guide for Prescribed and Wildland Fire 2001 Edition. Produced by the National Wildfire coordinating Group Fire Use Working Team.