Darken, v. t. [Imp. & p. p. Darkened; p. pr. & vb. n. Darkening.]
Etymology: [AS. deorcian. See Dark, a.]
1. To make dark or black; to deprite of light; to obscure; as, a darkened room. They [locusts] covered the face of the whole earth, so that the land was darkened. Ex. x. 15. So spake the Sovran Voice; and clouds began To darken all the hill. Milton.
2. To render dim; to deprive of vision. Let their eyes be darkened, that they may not see. Rom. xi. 10.
3. To cloud, obscure, or perplex; to render less clear or intelligible. Such was his wisdom that his confidence did seldom darkenhis foresight. Bacon. Who is this that darkeneth counsel by words without knowledge Job. xxxviii. 2.
4. To cast a gloom upon. With these forced thoughts, I prithee, darken not The mirth of the feast. Shak.
1 more senses
5. To make foul; to sully; to tarnish. I must not think there are Evils enough to darken all his goodness. Shak.
1 other Webster entry under this spelling
Darken, v. i.
To grow or darker.
Shades of meaning
Fernald lists darken only as an antonym, under bleach.
He lists it without comment; the entries above explain its neighbors.