From Science Europe Data Glossary
Definition: a data scientist is a practitioner of data science.
Explanation: data scientists investigate complex problems through expertise in disciplines within the fields of mathematics, statistics, and computer science. These areas represent great breadth and diversity of knowledge, and a data scientist will most likely be expert in only one or at most two of these areas and merely proficient in the other(s). Therefore a data scientist typically works as part of a team whose other members have knowledge and skills which complement his or hers. Data scientists use the ability to find and interpret rich data sources, manage large amounts of data despite hardware, software, and bandwidth constraints, merge data sources, ensure consistency of datasets, create visualizations to aid in understanding data, build mathematical models using the data, present and communicate the data insights/findings to specialists and scientists in their team and if required to a non-expert audience.