Weak Defense Against:
Ice (just think of it as frostbite, your teeth getting cold when biting into ice-cream, tissue freezing under ice, numbness, etc.)
Poison (poison in the bloodstream or on the bone marrow, tissues die)
Steel (if you hit your knee against steel, it'll hurt real bad. Steel can penetrate bone. Think chainsaw=metal claw)
Bug (it harvests on the bone, parasitism)

Strong Defense Against:
Normal (tackle bone, which is stronger than diamonds, and see if it hurts the bone)
Fighting (karate chop bone, and you'll break your hand)
Fire (can you burn bone? I don't think you can. Correct me if I'm wrong)
Rock (bone is a lot stronger than it)

Weak Attack Against:
Ice (look at why it has weak defense against it)
Ground (what're ya gonna do? Dig with bones until you finally get somewhere? No.)
Bug (idk, you attack it, it climbs up the bone and starts eating away at it?)

Strong Attack Against:
Steel (bone is stonger than it)
Rock (bone is stonger than it, but Rock really doesn't need another weakness)
Flying (same reason as Rock, to crush most birds and other flying creatures, and to hit it out of the sky)