The Collaborative International Dictionary of English v.0.48:
Preach \Preach\, v. i. [imp. & p. p. Preached; p. pr. & vb. n.
Preaching.] [OE. prechen, OF. preechier, F. pr[^e]cher, fr.
L. praedicare to cry in public, to proclaim; prae before +
dicare to make known, dicere to say; or perhaps from
(assumed) LL. praedictare. See Diction, and cf.
1. To proclaim or publish tidings; specifically, to proclaim
the gospel; to discourse publicly on a religious subject,
or from a text of Scripture; to deliver a sermon.
How shall they preach, except they be sent? --Rom.
From that time Jesus began to preach. --Matt. iv.
2. To give serious advice on morals or religion; to discourse
in the manner of a preacher.