The reason why I wanted to know was because I discovered some odd urls in Webmaster Tools that looked like search urls. So to find the answer to this question I first set up a page with 3 forms.
Form 1: Using the form GET method my page would get a new title and content if form was submitted. The URL would be different since I added a URL variable to the original URL.
Form 2: Using the form POST method. If this form was submitted the original page would have new content, just like search page.
Form 3: Using the form POST method but with a different action URL than the form page itself. I did this to check if Google would discover the “secret” action page.