INSEAD actually has a very concrete structure for this in their pdf (
https://mba.insead.edu/admissions/docume ... cy2016.pdf). Following their instructions, you can claim "practical" knowledge of a second language in your application, but you will have to take a competency test if accepted. There are posted deadlines for taking the competency test in advance of matriculation (June 1 for entering in September, for example). I have worked with applicants who have definitely treated this area as wishful thinking, and worked like crazy to get their competency up in advance of that deadline.
Bear in mind that you will need to develop competence in a third language while you are a student at INSEAD.
Good luck!
Margaret Strother
Stacy Blackman Consulting