My roommate's wifi password is just the ssid with a single-digit number appended. The ssid itself is a word that appears in the dictionary also with a single-digit number appended to it. E.g. his network might be called Dict-word6, with the password being something like Dict-word65.
I want to hop on his wifi but he stubbornly keeps brushing off my requests that he let me hard reset the router and switch to a high-entropy password. I'm wondering if I should just use it and not really worry? How likely is it that some hacker actually cracked his password? (He's not a target in the hacker world by any means, just a regular dude.)
Edit: my question evolved from how secure is it to how do I securely use it. Answers to the second point are in the comments.