I encountered many unique and interesting events today, such as my Windows user friend is using my Mac, my Mac cannot log out automatically, etc and from these incidents, I got more knowledge on operating my Mac, such that:
You should have known that using Command-Control-D you can mouse hover a word and directly see the definition of the word without the need to open your Mac Dictionary.
However, this trick is widely known. But I can't even find any single source talking about feature like Look Up in Thesaurus. Here is how to do it: