Everyone may have a slightly different answer when this question is posed to them but it is important to know what the interviewer is looking for in your answer when they ask this question. When you describe leadership it is important to keep in mind that one of the most important qualities in any leader is the ability to act as a visionary for their staff. A leader is ultimately the person who will set the course and establish the direction that others are to follow.
If you are being hired for a leadership or management role you should be able to act as a positive role model and set a good example that others in the company can follow. A leader must often be able to inspire others and encourage them to reach as high as they possibly can.
These are the types of attributes that you should describe in your answer when you are asked to define leadership. When answering this question you may also wish to briefly describe someone you consider to be an effective leader and highlight how they have been able to act as a leader based on those characteristics or traits.
Remember that you personally need not have had any prior leadership or management experience in order to accurately describe what makes a good leader. If you have ever worked under a good leader you will know it and will be able to discuss the way in which they led and inspired others to perform better and to behave in a responsible manner by setting a good example.
In asking this question the interviewer is seeking to find out how you view leadership and truly wants to know what you look for in a good leader. They could be asking this question because they want to find out more regarding what you look for in a good supervisor or if you are being considered for a management position they may be interested in finding out how you see yourself as a leader. Regardless, it is important to make sure that you give plenty of thought to this question and that you answer it in a manner that demonstrates your understanding of the most important qualities that a good leader can possess. No matter what type of position for which you are interviewing this will help you to answer the question positively and effectively.