Real Dictionary

lecture
countable noun: A lecture is a talk someone gives in order to teach people about a particular subject, usually at a university or college.
verb: If someone lectures you about something, they criticize you or tell you how they think you should behave.
verb: If you lecture on a particular subject, you give a lecture or a series of lectures about it.

lecture in American English
an informative talk given as before an audience or class and usually prepared beforehand
to give a lecture or lectures
to give a lecture to
intransitive verb: to give a lecture or series of lectures
noun: a speech read or delivered before an audience or class, esp. for instruction or to set forth some subject
transitive verb: to deliver a lecture to or before; instruct by lectures

lecture in British English
noun: a discourse on a particular subject given or read to an audience
verb: to give or read a lecture (to an audience or class)