› FINANCE, STOCK MARKET used to describe the shares, etc. to which something such as an option (= the right to buy or sell something in the future) relates: The option was sold requiring payment against delivery of the underlying security.
› ACCOUNTING, FINANCE used to describe the basic level or amount of something before anything else is added or taken away: Underlying conditions are favourable. They underestimated their underlying costs and ended up losing a lot of money. Last year the company had underlying earnings of $10.6m on $34m sales.