Specialise is a verb which means to focus on a particular area of expertise or activity. It is often used in the context of a job, where an individual focuses on a specific field or skill set. For example, a doctor may specialise in cardiology, or a lawyer may specialise in corporate law. Specialising can also be used in other contexts, such as a hobby or interest. For example, someone may specialise in collecting vintage cars or playing the guitar. In any case, specialising involves dedicating time and effort to a particular area of interest.