Source : Webster's Revised Unabridged Dictionary (1913)

Siesta \Si*es"ta\, n. [Sp., probably fr. L. sessitare to sit
   much or long, v. freq. of sedere, sessum, to sit. See {Sit}.]
   A short sleep taken about the middle of the day, or after
   dinner; a midday nap.

Source : WordNet®

siesta
     n : a nap in the early afternoon (especially in hot countries)