Webster's Revised Unabridged Dictionary · 1913

Explain

Explain (eks*plān") , transitive verb

[Latin explandare to flatten, spread out, explain; ex out + plandare to make level or plain, planus plain: compare Old French esplaner, explaner. See Plain,a., and compare Esplanade.]

1.
To flatten; to spread out; to unfold; to expand. [Obsolete]
The horse-chestnut is... ready to explain its leaf. — Evelyn
2.
To make plain, manifest, or intelligible; to clear of obscurity; to expound; to unfold and illustrate the meaning of; as, to explain a chapter of the Bible.
Commentators to explain the difficult passages to you. — Gay
Collocations (1)
To explain away , to get rid of by explanation. Those explain the meaning quite away. — Pope

Explain , intransitive verb

To give an explanation.