If something is nefarious, it is criminal, evil, malicious and/or wicked. Thinking of superheroes can help you remember the meaning of the word, but it is often used in much less exciting circumstances. News reporters investigate corrupt politicians in order to uncover the nefarious activities. And, if you don't pay for your downloaded music, you have gotten it by nefarious means.

Now, if you find this word interesting, please use it as needed.

More Info: www.merriam-webster.com