When describing my job, I often explain it shortly as:

‘Simplifying complexity to facilitate customer-centric decision making’.

While the bit more elaborate version is:

‘Analysing complex scenarios by the use of design activities that focus on listening to both customers, employees and stakeholders in order to create a holistic understanding of the interactions a customer or employee has with a brand and its service.

These derived insights are communicated both visual and actionable, to consequently enable cross-functional teams deliver the ideal service experience’.

In case you’re familiar to common buzzwords, I’d divide my expertise as: 
Experiment Design  |  CX Strategy  |  Service Design  | 
User Research  |  UX Design