A word that can be its own antonym is called a contronym. Cleave can mean to sever or to cling. Buckle can mean to fasten (buckle your seat belt) or to bend (the shelf buckled under the weight of all the books)
You can burn calories in lots of ways. For example, banging your head against a wall burns 150 calories an hour. Sitting still afterward contemplating the pain probably burns about as many.
Cherophobia is the fear of fun or aversion to happiness. That’s sad. Which I guess would make someone suffering from cherophobia happy.
Movie trailers were originally shown after the movie, which is why they were called “trailers”.