An anti-dilution protection mechanism whereby the conversion rate of preferred stock is adjusted in order to reduce an investor's loss due to an increase in the number of shares in a company. Without a ratchet, an investor would suffer from a dilution of his or her percentage ownership. Usually as a result of the implementation of a weighted average ratchet, company management and employees who own a fixed amount of common shares suffer significant dilution, but not as badly as in the case of a full ratchet.