n. 1 the soft glowing light from the sky when the sun is below the horizon, esp. in the evening. 2 the period of this. 3 a faint light. 4 a state of imperfect knowledge or understanding. 5 a period of decline or destruction. twilight sleep Med. a state of partial narcosis, esp. to ease the pain of childbirth. twilight zone 1 an urban area that is becoming dilapidated. 2 any physical or conceptual area which is undefined or intermediate.
[ ME f. OE twi- two (in uncert. sense) + LIGHT(1) ]