Source : Webster's Revised Unabridged Dictionary (1913)

Deflate \De*flate"\, v. t. [Pref. de- down + L. flare, flatus to
   blow.]
   To reduce from an inflated condition.

Source : WordNet®

deflate
     v 1: collapse by releasing contained air or gas; "deflate a
          balloon"
     2: release contained air or gas from; "deflate the air
        mattress"
     3: reduce or lessen the size or importance of; "The bad review
        of his work deflated his self-confidence" [syn: {puncture}]
     4: produce deflation in; "The new measures deflated the
        economy" [ant: {inflate}]
     5: reduce or cut back the amount or availability of, creating a
        decline in value or prices; "deflate the currency" [ant: {inflate}]
     6: become deflated or flaccid, as by losing air; "The balloons
        deflated" [ant: {inflate}]

Source : Free On-Line Dictionary of Computing

deflate
     
         A {compression} {standard} derived
        from {LZ77}; it is reportedly used in {zip}, {gzip}, {PKZIP},
        and {png}, among others.
     
        Unlike {LZW}, deflate compression does not use patented
        compression {algorithms}.
     
        Used as a verb to mean to compress (not decompress!) a file
        which has been compressed using deflate compression.  The
        opposite, {inflate}, means to decompress data which has been
        deflated.
     
        Deflate is described in {RFC 1951}.
     
        (1997-06-21)