›an amount of money that you pay to a lawyer, consultant (= someone paid to give expert advice or training), etc. in order to be sure that they can work for you when you need them to: The firm retained White as a consultant, paying him a $5,000 retainer.get/be on/receive a retainerPenn's firm is on a retainer of $15,000 to $20,000 per month.An elite 15% of all headhunters are on retainer, reaping two-thirds of their pay up front.an annual/monthly retainer