In journalistic parlance, spiking refers to withholding a story from publication for reasons pertaining to its veracity (whether or not it conforms to the facts). Spiking is relatively rare and usually happens late in the editing process (after the assigning editor has signed off on it). It is only required when a simple edit or questioning the reporter or assigning editor cannot fix the problem.
Reasons for spiking include a clear bias (someone on an opposing side of an issue did not respond, despite the fact that said response is central to the story), a major hole (many, if not most, readers will have a question after reading the story), a sudden change in events (three more people have died, but getting details from officials is impossible on deadline), or suspicions of plagiarism or other ethical violations on the part of the author.
In some cases, a story may be spiked if it is deemed to conflict with the commercial interests of the newspaper's publisher: if, for example, it concerns a company with which the publisher has a close relationship. This is more likely at a local level, where small newspapers are dependent on advertising revenue from businesses such as estate agents and recruitment agencies.
Stories are spiked for other reasons, but the decision is not taken lightly, as a valid, usually detailed explanation will be solicited by those further up the chain of command, often at the behest of the reporter.