sharpen
     v 1: make sharp or sharper; "sharpen the knives" [ant: {dull}]
     2: make sharp or sharper; "We had to sharpen our arguments"
     3: become sharp or sharper; "The debate sharpened"
     4: put (an image) into focus; "Please focus the image; we
        cannot enjoy the movie" [syn: {focus}, {focalize}, {focalise}]
        [ant: {blur}]
     5: make (images or sounds) sharp or sharper [ant: {soften}]
     6: raise the pitch of (musical notes) [ant: {flatten}]
     7: give a point to; "The candles are tapered" [syn: {taper}, {point}]
     8: make (one's senses) more acute; "This drug will sharpen your
        vision" [syn: {heighten}]
Source: WordNet® 2.0