pro rata(a pro rata payment or share in something is calculated according to exactly how much of something is used, how much work is done etc: • The residents here pay more than their pro rata share of taxes. • Fees for longer or shorter courses are calculated on a pro rata basis. – pro rata adverb : • The company directors are required to allot the shares to existing shareholders pro rata to the number of shares owned. LBED Alexander Demidov)