When a woman (or man) is fellating another man (or woman) and there are other parties involved in conversation with, or adjacent to the recipient that are not privy to the current action.
That bitch done gave me head under the dinner table, call that top secret. (with some heavy 808's and trap style beat)
A color of paint that is TOP SECRET. Though there are many requests for the "color code" for Top Secret Gold paint, no such code exists nor is it available from any paint or body shop. This color is a custom blend made from only the finest materials. The paint is usually available for around $500 per quart, pending the approval of the vehicle it is to be used on.