Idle Card
An idle card is a card that adds no value to a hand. It does not help make a pair, straight, flush or any other combination.
The simple explanation
If you hold a pair and a useless fifth card, that fifth card is idle. In a draw, the card that does not help the draw is also idle.
A closer look
The word is useful in discussion of drawing hands and starting hands. A hand with many idle cards is weak. For example, in stud, a card that does not connect with your up cards or your pair adds nothing. Good starting hands usually have cards that work together, so there are fewer idle cards.
A practical example
A player has K♥ K♦ and the board is 9♣ 4♠ 2♦. The nine, four and two are idle for him because they do not improve his pair.
Full explanation
An idle card is a card that adds no value to a hand. It does not help make a pair, straight, flush or any other combination.
An idle card adds no value to a hand.
It does not help make a combination.
Hands with many idle cards are weak.
Good hands have cards that work together.