What is "head crash"

n. (context computing English) A collision of the head of a hard drive with the platter, resulting in permanent damage to the hard drive.

n. (computer science) a crash of a read/write head in a hard disk drive (usually caused by contact of the head with the surface of the magnetic disk)

A head crash is a hard-disk failure that occurs when a read–write head of a hard disk drive comes in contact with its rotating platter, resulting in permanent and usually irreparable damage to the magnetic media on the platter surface. It is most commonly caused by a sudden severe motion of the disk, for example the jolt caused by dropping a laptop to the ground while it is operating or physically shocking a computer.