Massive amounts of data that are difficult to manage and analyze using traditional software and hardware. In health care, examples of sources for Big Data include electronic medical records, administrative records, prescription data, wearable devices, medical images, laboratory results, and genomic profiles.
Raghupathi, W and Raghupahti, V. Big Data Analytics in healthcare: promise and potential. Health Information and Science Systems 2014, 2:3. Link to article