Making a pair with the middle-ranked card on the flop and a hole card. For example, on a board of A-9-2, you have middle pair if one of your hole cards is a 9 (excluding A9 and 92, which give you two pair).
Making a pair with the middle-ranked card on the flop and a hole card. For example, on a board of A-9-2, you have middle pair if one of your hole cards is a 9 (excluding A9 and 92, which give you two pair).