Tending to think about or discuss sexual or lewd topics or interpret mundane things in such a way. I wasn't referring to sex at all, and you know it—quit being so dirty-minded!
dirty-minded
mod. having a tendency to see the lewd or obscene aspects of anything; having a tendency to place an obscene interpretation on the words and actions of others. Sam is sort of dirty-minded, but he wouldn’t do anything really vile.