In a surreptitious manner; stealthily, furtively, secretly.

Stealthy, furtive, well hidden, covert (especially movements).

The state or quality of being surreptitious.

An instance of the practice described under surreptitious advertising.

plural of surreptitious advertisement

The representation in words or pictures of goods, services, the name, the trade mark or the activities of a producer of goods or a provider of services in media products when such representation is intended by the publisher to serve advertising and might mislead the public as to its nature.