lessen
     v 1: decrease in size, extent, or range; "The amount of homework
          decreased towards the end of the semester"; "The cabin
          pressure fell dramatically"; "her weight fall to under a
          hundred pounds"; "his voice fell to a whisper" [syn: {decrease},
           {diminish}, {fall}] [ant: {increase}]
     2: make smaller; "He decreased his staff" [syn: {decrease}, {minify}]
        [ant: {increase}]
     3: wear off or die down; "The pain subsided" [syn: {subside}]
Source: WordNet® 2.0