Quick answer
Miley is a girl name.
Meaning and history
In the case of actress and singer Miley Cyrus (1992-), it is a shortened form of the nickname Smiley, given to her by her father because she often smiled. Although it was not at all common before she brought it to public attention, there are some examples of its use before her time, most likely as a diminutive of Miles.
Notes and context
Usage: english