Conditionally Unstable
Conditional instability occurs when the environmental lapse rate is between the DALR and SALR. For example, say the environmental lapse rate is 8 degrees C per 1000m, between 10 degrees and 6 degrees C per 1000m of the DALR and SALR respectively. If a parcel of unsaturated air were to rise, it would follow the DALR and would be colder at each level than the air around it. It would therefore sink back to its original position as it is in stable atmosphere. However, if a parcel of saturated air were to rise it would follow the SALR, the rising air would be warmer than its surroundings and, once given a push upward, would continue to move in that direction: the atmosphere in this case in unstable for saturated air. Overall, in this example the atmosphere is said to be conditionally unstable. Whether the atmosphere is stable or not depends on whether the parcel of air is unsaturated or saturated.
The average lapse rate in the troposphere is about 6.5 degrees C per 1000m. As this lies between the DALR and the SALR the atmopshere is normally is a state of conditional instability.