1. To raise and scrunch the shoulders up by the ears. In this usage, a noun or pronoun can be used between "hunch" and "up." Would you stop hunching up your shoulders like that? Try to relax!
2. To bring the limbs in close to the body; to curl up. I pulled the blanket over me and hunched up to try to keep warm.
hunch something up
to raise up or lift up some body part, usually the shoulders. He hunched his shoulders up in his effort to get warm. He hunched up his shoulders to keep warm.
to squeeze or pull the parts of one's body together. He hunched up in a corner to keep warm. Why is that child hunched up in the corner?