Any page or site can be re-submitted to a search engine or directory. Re-submission of critical pages at given accepted intervals is necessary for some search engines; however, with most directories, once the domain has a listing, it should not be re-submitted.
Repeating the search engine registration process one or more times for the same page or site. Under certain circumstances, this is regarded with suspicion by the search engines, as it could indicate that someone is experimenting with spamming techniques.
The process of submitting a web page to a search engine and then repeating the submission process - either a couple of times or regularly over a period of time. Contrary to popular belief, regular re-submission does not improve a page's ranking and is considered a form of spamdexing by most search engines.