A pocket pair that ranks lower than the three cards on the flop.

a pocket pair that is smaller than any card on the board

Matching hole cards smaller than an opponentÂ's holdings or the cards on the board.

Any pair that is lower than the highest card on the board (especially those that are lower than all the cards on the board). If you hold 33 and the board is showing KJ6, you have an underpair. See also: Overpair.