Webster's Revised Unabridged Dictionary · 1913

Intensify

Intensify , transitive verb

[Intense + -fly.]

To render more intense; as, to intensify heat or cold; to intensify colors; to intensify a photographic negative; to intensify animosity. — Bacon
How piercing is the sting of pride By want embittered and intensified. — Longfellow

Intensify , intransitive verb

To become intense, or more intense; to act with increasing power or energy.