• Unstructured data (or unstructured information) refers to masses of (usually) computerized information which do either not have a data structure or one that is not easily readable by a machine. The term is imprecise: software that creates machine-processable structure exploits word morphology, sentence syntax, and other small- and large-scale patterns found in source materials to discern linguistic, auditory, and visual structure that is inherent in all forms of human communication.
      (Fonte: Wikipedia)

• Unstructured information represents the vast majority of the data collected and accessible to enterprises. This data may be in various formats and may lack the organization of traditional sources such as database records. Exploiting this information requires systems for managing and extracting knowledge from large collections of unstructured data and applications for discovering patterns and relationships.
      (Fonte: IBM System Journal - Unstructured Information Management - Vol. 43, No. 3, 2004)

Dal nostro punto di vista, è informazione non strutturata quella che richiede un trattamento per potere essere utilizzata in forma aggregata.