The American Marketing Association
defines Marketing Research as...
"Marketing research is the function which links the consumer, customer, and public to the marketer through information--information used to identify and define marketing opportunities and problems; generate, refine, and evaluate marketing actions; monitor marketing performance; and improve understanding of marketing as a process."
"Marketing research specifies the information required to address these issues; designs the method for collecting information; manages and implements the data collection process; analyzes the results; and communicates the findings and their implications."
"Marketing research is the process of obtaining knowledge and gaining an understanding about what people think, feel and do in relationship to meeting their needs, desires and preferences.
In plain English, it's determining what customers and prospects think about your company, its services and products, and how your company can better serve them.