What is "to leave one out in the cold"

Cold \Cold\, n.

1. The relative absence of heat or warmth.

2. The sensation produced by the escape of heat; chilliness or chillness.

   When she saw her lord prepared to part, A deadly cold ran shivering to her heart.
   --Dryden.

3. (Med.) A morbid state of the animal system produced by exposure to cold or dampness; a catarrh.

   Cold sore (Med.), a vesicular eruption appearing about the mouth as the result of a cold, or in the course of any disease attended with fever.

   To leave one out in the cold, to overlook or neglect him.