This really needed to be said.
What this cartoon isn't trying to say:
Everything you learned from dictionaries is ABSOLUTELY WRONG.
When I was young, I used to love reading the dictionary. It really helped me learn a lot of new words.
What this cartoon is actually trying to say:
It's not about being "right" or "wrong." The definitions the dictionary gives are not black and white.
While the dictionary might help out for very basic definitions, let's remember those definitions are watered down, short, quick, and often lacking nuance. Dictionary definitions won't necessarily tell you how a word has transformed in society.
And it never hurts to give a closer look to who wrote something. After all, everyone is a little biased. Even dictionary-writers.