A number of researchers have sought to understand what enables the 'expert' professional to achieve a rapid and effortless understanding of presenting situations. Central to many of the explanations offered is the term 'intuition'. It might be thought, therefore, that the word describes a coherent concept embracing certain related features and used with consistency. A study of the literature suggests that this is not so. 'Intuition' is more than a contested concept, it is also used in ways that lack both clarity and coherence. Some of the confusion associated with the concept seems to stem from the belief that intuition is an irrational process. As a consequence, it is assumed that intuition can be neither fully understood nor explained. In this paper we discuss a number of issues relating to the nature of 'intuition'. We argue that intuition may be understood as an irrational process that has a rational basis. Intuitive thinking has certain essential features and involves the use of a sound, rational, relevant knowledge base in situations that, through experience, are so familiar that the person has learned how to recognize and act on appropriate patterns.