Webster's Revised Unabridged Dictionary · 1913

Sharpen

Sharpen , transitive verb

[See Sharp, a.]

To make sharp.
(a)
To give a keen edge or fine point to; to make sharper; as, to sharpen an ax, or the teeth of a saw.
(b)
To render more quick or acute in perception; to make more ready or ingenious.
The air... sharpened his visual ray To objects distant far. — Milton
He that wrestles with us strengthens our nerves and sharpens our skill. — Burke
(c)
To make more eager; as, to sharpen men's desires.
Epicurean cooks Sharpen with cloyless sauce his appetite. — Shakespeare
(d)
To make more pungent and intense; as, to sharpen a pain or disease.
(e)
To make biting, sarcastic, or severe.
(f)
To render more shrill or piercing.
Sharpen each word. — E. Smith
Inclosures not only preserve sound, but increase and sharpen it. — Bacon
(g)
(Music) To make more tart or acid; to make sour; as, the rays of the sun sharpen vinegar.
(h)
(Music) To raise, as a sound, by means of a sharp; to apply a sharp to.

Sharpen , intransitive verb

To grow or become sharp.