a talk that is given to a group of people to teach them about a particular subject, often as part of a university or college course

a long, angry talk that somebody gives to one person or a group of people because they have done something wrong

I know I should stop smoking—don't give me a lecture about it.

to give a talk or a series of talks to a group of people on a subject, especially as a way of teaching in a university or college

to criticize somebody or tell them how you think they should behave, especially when it is done in an annoying way

He's always lecturing me about the way I dress.

She lectured me about taking responsibility for my actions.

LEARNit Dictionary