The innate sense which allows one who possesses it to find the restroom in a public building (e.g., restaurant, DMV
, other place of business, et cetera) or even private home without being given directions. Some people have it, some do not.
To test if you have a bathroom sense, simply get up from your table at a restaurant you've never previously relieved yourself at and head in the direction you think the restroom is. If you are able to semi-consistently locate the bathroom, pulled by some natural gut feeling, congratulations.