A signaled (SD) contingency for behavior that indicates that engaging in the behavior will prevent and/or delay the onset of an aversive stimulus.

Hint: In Los Angeles, when the weather report signals rain, people stay home. That is the discriminated avoidant behavior. In test questions, look for a signal or warning, and the avoidant behavior. Both need to be there. 

6th Edition TCO

B.4 Identify and distinguish between positive and negative reinforcement contingencies.