To lie under; to rest beneath; to be situated under; as, a stratum of clay underlies the surface gravel. [1913 Webster]
To be at the basis of; to form the foundation of; to support; as, a doctrine underlying a theory. [1913 Webster]
To be subject or amenable to. [1913 Webster]
"The knight of Ivanhoe . . . underlies the challenge of Brian der Bois Guilbert." [1913 Webster]

underlie, v. i.

To lie below or under. [1913 Webster]

underlie, n.

See Underlay, n., 1. [1913 Webster]

top

OXFORD DICTIONARY

underlie, v.tr. (-lying; past -lay; past part. -lain)
1 (also absol.) lie or be situated under (a stratum etc.).
2 (also absol.) (esp. as underlying adj.) (of a principle, reason, etc.) be the basis of (a doctrine, law, conduct, etc.).
3 exist beneath the superficial aspect of.

Etymology

OE underlicgan (as UNDER-, LIE(1))

top

THESAURUS

underlie

afford support, back, back up, be latent, bear, bear up, bed on, bolster, bolster up, bottom on, brace, build on, buoy up, buttress, carry, couch, cradle, crawl, crouch, crutch, cushion, escape notice, found on, give support, ground on, grovel, hibernate, hold, hold up, hug the earth, keep afloat, keep up, lend support, lie beneath, lie dormant, lie hid, lie low, lie prone, lie prostrate, lie under, lurk, mainstay, maintain, make no sign, pillow, prop, reinforce, set on, shore, shore up, shoulder, smolder, squat, stay, subsidize, subvention, support, sustain, underbrace, undergird, underpin, underset, upbear, uphold, upkeep

top

ROGET THESAURUS

underlie

Lowness

VB be low, lie low, lie flat, underlie, crouch, slouch, wallow, grovel, lower.

Implication

VB be latent, lurk, smolder, underlie, make no sign, escape observation, escape detection, escape recognition, lie hid, laugh in one's sleeve, keep back, involve, imply, understand, allude to, infer, leave an inference, entail, whisper, read between the lines.

For further exploring for "underlie" in Webster Dictionary Online