Which of the following correctly defines the term "loitering" according to the provided content?

The correct definition of "loitering" is the act of idling in public areas with the intent to commit a crime. This definition emphasizes the notion that merely being in a location isn't an issue unless there is an underlying intent to engage in unlawful activity. The concept of loitering involves not just the physical presence in a place but also the motivations behind that presence. Authorities often regulate loitering to deter potential criminal behavior and maintain public order.

The other options do not capture this critical element of intent. For instance, simply waiting for a friend or hanging around public facilities does not inherently imply any unlawful activity or intention. Being in a place without purpose is somewhat closer but fails to communicate the critical aspect of potential criminal intent, which is a defining characteristic of loitering in legal contexts. Hence, option D accurately encapsulates the association between loitering and the potential for crime.