A price quote on a security, made by a dealer or market maker, that guarantees a bid or ask price up to the amount quoted. This differs from a nominal quote wherein the price and quantity of a bid or ask quote are not firmly posted.
For example, if a market maker posts a bid firm price quote of $25 @ 10K, this tells other dealers and investors that this market maker will buy up to 10,000 shares for a price of $25. If the quote were to be nominal, then the seller of the security could try to negotiate for a better price and the market maker might move on its price - for example, being willing to purchase for $25.75.