Meaning of inside straight

in'side straight'

Pronunciation: [key]
  1. a set of four cards, as the five, seven, eight, and nine, requiring one card of a denomination next above or below the second or third ranking cards of the set to make a straight.
  2. to build up hopes for something that has little or no chance of happening.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.