Is there a Unix command to echo out an entire dictionary?

I'm writing a program that uses regular expressions to make comparisons against the entire dictionary on the UNIX shell. Is there a way that I can echo some sort of predefined dictionary and then pipe it to grep? I was thinking I could use the backend of some programs spell-checker? Or do I just need to echo a file of words? If so, where can I find an english dictionary, with one word per line?