Source : Webster's Revised Unabridged Dictionary (1913)

Alcaid \Al*caid"\, Alcayde \Al*cayde"\ ([a^]k*k[=a]d"; Sp.
   [aum]l*k[aum]*[-e]"d[asl]), n. [Sp. alcaide, fr. Ar.
   al-q[=a][=i]d governor, fr. q[=a]da to lead, govern.]
   1. A commander of a castle or fortress among the Spaniards,
      Portuguese, and Moors.

   2. The warden, or keeper of a jail.