It means connecting well with other employees or customers in rapidly changing environments, thereby achieving highly collective performance. The two main components of Social Agility are Enterprise Social Density and Enterprise Social Visibility.
It is part of the Five Dimensions of Enterprise Agility (Cake Model) and Leading Exponential Change, published initially in 2018. It is also part of the Enterprise Agility Framework. It provides a systemic view of any situation using social theories and ideas.
For more detailed information about Social Agility, check Enterprise Agility Fundamentals, Chapter 6, page 245.