Source : Webster's Revised Unabridged Dictionary (1913)

Silo \Si"lo\, n. [F.]
   A pit or vat for packing away green fodder for winter use so
   as to exclude air and outside moisture. See {Ensilage}.

Source : WordNet®

silo
     n 1: a cylindrical tower used for storing silage
     2: military installation consisting of an underground structure
        where ballistic missiles can be stored and fired

Source : Free On-Line Dictionary of Computing

silo
     
        The {FIFO} input-character buffer in an {EIA-232} serial line
        card.  So called from {DEC} terminology used on DH and DZ line
        cards for the {VAX} and {PDP-11}, presumably because it was a
        storage space for fungible stuff that went in at the top and
        came out at the bottom.