Real Dictionary

sharpen
verb: If disagreements or differences between people sharpen, or if they are sharpened, they become bigger or more important.
verb: If you sharpen an object, you make its edge very thin or you make its end pointed.
verb: If your senses, understanding, or skills sharpen or are sharpened, you become better at noticing things, thinking, or doing something.

sharpen in American English
to make or become sharp or sharper

sharpen in British English
verb: to make or become sharp or sharper