1. To rub someone's foot or feet with one's own, usually in secret beneath a table as a means of flirting or indicating romantic or sexual interest. My friend's sister started playing footsie with me during dinner. I had no idea she was into me! Are you two playing footsies?

2. By extension, to become secretly involved with someone; to offer clandestine cooperation with someone to gain their favor. It's been revealed that the senator has been playing footsie with major corporations to bypass federal regulations and bureaucratic red tape.