'black hole' definitions:

Definition of 'black hole'

noun

A region of space resulting from the collapse of a star; extremely high gravitational field

From: GCIDE

black hole \black" hole`\ A dungeon or dark cell in a prison; a military lock-up or guardroom; -- now commonly with allusion to the cell (the Black Hole) in a fort at Calcutta (called the {Black Hole of Calcutta}), into which 146 English prisoners were thrust by the nabob Suraja Dowla on the night of June 20, 1765, and in which 123 of the prisoners died before morning from lack of air. [1913 Webster]
A discipline of unlimited autocracy, upheld by rods, and ferules, and the black hole. --H. Spencer. [1913 Webster]
2. (Physics, Astron.) An astronomical object whose mass is so condensed that the gravitational force does not allow anything, even light, to escape from its outer limit (the event horizon). The existence of such objects was first proposed from theoretical considerations. Because light cannot escape from such objects, they have not yet been detected with certainty (1998), but several "candidates" have been observed whose properties strongly suggest that they are black holes. Some theorists suggest that the centers of many galaxies may have large black holes at their cores. See also escape velocity. [PJC]
3. [from the astronomical black hole.] a place into which things may enter, but can never emerge. [Fig., Jocose] "He was so disorganized his office was a black hole." [PJC]