A non-jump rebid in a new suit that takes the bidding above the level of two of your original suit, usually in a higher-ranking suit. Any player can reverse, though the term most commonly applies to a reverse by opener. In the first three of the sequences shown below, the last bid shown is a reverse.
The 2♠ bid in the fourth sequence is not a reverse; this is because the 2♦ response had already taken the bidding above the level of 2♣.
When a reverse is in a higher- ranking suit, the first bid suit will always be longer than the second suit. A reverse nearly always shows values beyond those already promised.