noun ·see underlay, ·noun, 1.
2. underlie ·vi to lie below or under.
3. underlie ·vt to be subject or amenable to.
4. underlie ·vt to lie under; to rest beneath; to be situated under; as, a stratum of clay underlies the surface gravel.
5. underlie ·vt to be at the basis of; to form the foundation of; to support; as, a doctrine underlying a theory.