A kind of articulation used by the natives of Southern
   Africa, consisting in a sudden withdrawal of the end or some other
   portion of the tongue from a part of the mouth with which it is in
   contact, whereby a sharp, clicking sound is produced. The sounds are
   four in number, and are called cerebral, palatal, dental, and lateral
   clicks or clucks, the latter being the noise ordinarily used in urging
   a horse forward.