A strong password should appear to be a random string of characters to an attacker. It should be 14 characters or longer, (eight characters or longer at a minimum). It should include a combination of uppercase and lowercase letters, numbers, and symbols.
From what I have been reading it seems that the "Standard" password - 8 character, alpha-numberic, both upper & lower case plus symbols is not considered strong enough. What is considered to be a strong password.