To wind (s.t. around s.t.); to wind around s.t. (pa-).
The -un imp. focuses on the object that is having s.t. wound around it. The -an and pa--un imperatives focus on the object that is being wound around s.t. The -an imp. is used primarily for just winding line around s.t. with no specific purpose other than to store line. The pa--un imp. is used when the line is serving a purpose for being wound around s.t. (as when securing a boat to a wharf).
Who wound this rope around a post?
That vine is winding around that mango tree.