doldrums

Concise Oxford English Dictionary © 2008 Oxford University Press:
doldrums /ˈdɒldrəmz/

▶plural noun (the doldrums)

• 1 a state of stagnation or depression.

• 2 an equatorial region of the Atlantic Ocean with calms, sudden storms, and light unpredictable winds.

– origin C18 (as doldrum ‘dull, sluggish person’): perh. from dull.