1. [v]  be or form the base for
2. [v]  lie underneath

UNDERLIE is a 8 letter word that starts with U.

1. \Un`der*lie"\, v. t. [AS. underlicgan. See {Under}, and
   {Lie} to be prostrate.]
   1. To lie under; to rest beneath; to be situated under; as, a
      stratum of clay underlies the surface gravel.
   
   2. To be at the basis of; to form the foundation of; to
      support; as, a doctrine underlying a theory.
   
   3. To be subject or amenable to. [R.]
   
            The knight of Ivanhoe . . . underlies the challenge
            of Brian der Bois Guilbert.           --Sir W.
                                                  Scott.
   
   

2. \Un`der*lie"\, v. i.
   To lie below or under.
   
   

3. \Un"der*lie`\, n.
   See {Underlay}, n., 1.