classified advertisement

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. An advertisement, usually brief and in small type, printed in a newspaper or magazine under headings with others of the same category.

Wiktionary

1. n. Any of a list of newspaper or website advertisements included with others under a heading describing the category of product or service offered.

WordNet 3.0

1. n. a short ad in a newspaper or magazine (usually in small print) and appearing along with other ads of the same type