Calming signals are small body language cues dogs use to defuse tension, either in themselves or in another dog or person nearby. The term was popularised by Norwegian trainer Turid Rugaas, though the behaviours themselves have always been part of normal dog communication.
Examples include a lip lick, a yawn, turning the head away, moving slowly, or sniffing the ground, often shown when a dog feels mildly uncomfortable or is trying to signal to another dog that they mean no harm.