https://www.google.com/#q=public+domain+english+word+list
2nd result quite relevant.
Could generate it, possibly like this: https://github.com/rspeer/wiki2text
Edit:
Applying this code to the example output from the wiki2text repo:
String input = new String(Files.readAllBytes(Paths.get("text.txt")));
System.out.println(Arrays.stream(input.split("\\s+"))
.filter(s -> s.matches("[a-zA-Z][a-z]*"))
.map(s -> s.toLowerCase())
.distinct()
.sorted()
.collect(Collectors.joining("\n")));
Yields the following: http://pastebin.java-gaming.org/90cc2436a2917
Could be useful.