Twilight

Twilight
–noun

1.	the soft, diffused light from the sky when the sun is below the horizon, either from daybreak to sunrise or, more commonly, from sunset to nightfall.

2.	the period in the morning or, more commonly, in the evening during which this light prevails.

3.	a terminal period, esp. after full development, success, etc.: the twilight of his life.

4.	a state of uncertainty, vagueness, or gloom.

–adjective

5.	of, pertaining to, or resembling twilight; dim; obscure: in the twilight hours.

6.	appearing or flying at twilight; crepuscular.

Example: "in the twilight of his career" means his career is starting to go down
Source: http://dictionary.com