Meaning of “lesson” - Learner’s Dictionary

lesson

noun [ C ] uk us /ˈlesən/
SCHOOL

A1 a period of time when a teacher teaches people:

The best way to improve your game is to take lessons.
She gives French lessons.
Lessons start at 9 a.m.
EXPERIENCE

B2 an experience that teaches you how to behave better in a similar situation in the future:

My parents made me pay back all the money, and it was a lesson I never forgot.

(Definition of “lesson” from the Cambridge Learner’s Dictionary © Cambridge University Press)