Source : Free On-Line Dictionary of Computing

balanced tree
     
         An optimisation of a {tree} which aims to keep
        equal numbers of items on each {subtree} of each node so as to
        minimise the maximum path from the root to any {leaf node}.
        As items are inserted and deleted, the tree is restructured to
        keep the nodes balanced and the search paths uniform.  Such an
        {algorithm} is appropriate where the overheads of the
        reorganisation on update are outweighed by the benefits of
        faster search.
     
        A {B-tree} is a kind of {balanced tree} that can have more
        than two subtrees at each node (i.e. one that is not
        restricted to being a {binary tree}).
     
        (2000-01-10)