Definition - What does Tombstone mean?
Tombstones are grave-looking, simple print advertisements in black and white that are used to make an announcement. Generally, they are placed by investment bankers to announce an initial public offering (IPO) or placement of a company's stock. They do not make an offer to sell nor do they solicit an offer to buy; they simply make the announcement and may specify where the details are available.
Divestopedia explains Tombstone
A tombstone is an advertisement that must meet the specific legal requirements and regulations imposed on the industry/professional represented in the advertisement. In the context of financial institutions, a tombstone formally announces a particular transaction. Tombstones get their name because of the style of the advertisement. They are made up of simple, centered text with a large amount of white space and lack any image or other visual embellishments. Such advertisements typically provide the bare bones information about the subject to the investors. For example, an advertisement detailing a new issue of security could specify where the prospectus may be obtained and information about the underwriting syndicate responsible for placing the new issue with investors.
Sometimes, investment banks use tombstones as a promotional tool. An investment bank may place an advertisement to announce its role in a private placement, corporate merger or acquisition. It is published after the issue has been sold.