Fig. [bought or sold] in secret or illegally. (Compare this to over the counter.) The drugstore owner was arrested for selling liquor under the counter.The clerk sold dirty books under the counter.
if something is bought or sold under the counter it is bought or sold secretly or in a way that is not legal Many of his books are banned and only available under the counter.
Secretly, surreptitiously, as in I'm sure they're selling liquor to minors under the counter. This expression most often alludes to an illegal transaction, the counter being the flat-surfaced furnishing or table over which legal business is conducted. It was first recorded in 1926. Also see under the table.