- Underlie is defined as to be under, or be the grounds for something.
- An example of underlie is laying under the shade of a tree.
- An example of underlie is a birth being the reason why someone is receiving a gift.
transitive verbun·der·lay , un·der·lain , un·der·ly·ing, un·der·lies
- To be located under or below.
- To be the support or basis of; account for: Many factors underlie my decision.
- To constitute a prior claim over.
(third-person singular simple present underlies, present participle underlying, simple past underlay, past participle underlain)