Source : Free On-Line Dictionary of Computing

cache line
     
         (Or cache block) The smallest unit of memory than
        can be transferred between the {main memory} and the {cache}.
     
        Rather than reading a single word or byte from main memory at
        a time, each cache entry is usually holds a certain number of
        words, known as a "cache line" or "cache block" and a whole
        line is read and cached at once.  This takes advantage of the
        principle of locality of reference: if one location is read
        then nearby locations (particularly following locations) are
        likely to be read soon afterward.  It can also take advantage
        of {page-mode} {DRAM} which allows faster access to
        consecutive locations.
     
        (1997-01-21)