The adjective insensible is used to describe someone who is unconscious. If you keep your bowling ball on the top shelf of the closet and it rolls out and conks you on the head, you will be probably rendered insensible.
The adjective insensible describes a lack of emotional response or being indifferent. If your friend says that the roller coaster was so scary it nearly made him vomit and you shrug and say, "Eh, it was okay," he may think you are insensible to fear. A lack of physical sensation can also be described as insensible. If your nerve endings are not acute and you don't feel much pain, you are insensible to pain. This can be dangerous, though, because you might not notice if you get hurt skateboarding.