As in Playing footsie (under the table)

The act of flirting in which one secretly touches the feet or legs of another with one's own, as under a table.

the act of kicking each other playfully under something that would usually hide it. usually it is given away by facil expressions such as laughing.

While footsie can be used to flirt with someone, it is also a direct game. In this game the participants sit across from each other and tickle each other's feet with their toes. It is sometimes (rarely though) used along side {bondage}