1. Lit. to bring someone to an abrupt halt by a heavy blow to the body, presumably knocking the person's wind out. (Alludes to a ship being slowed by positioning another ship to block off the wind from the first ship's sails.) Fred hit Mike and really knocked the wind out of his sails. Fred ran into the side of the garage and knocked the wind out of his sails.

2. Fig. to humiliate someone. The sharp rebuke from the boss knocked the wind out of his sails. That scolding really knocked the wind out of her sails.