‘To grind’ is a very interesting word. You probably know its core meaning ‘ to crash’, or ‘to rub’.
And it is the ‘rubbing’ meaning that originated some slang phrases. As it means ‘to rub an object against a hard surface’ ... in American English grind means a type of dance typically involving woman( women) rubbing their b*****s against a man’s area. ( supposedly against their harder area 😅). That’s the meaning in your book as a song is being mentioned.
‘Back it the college days, grinding on the dance floor was really common. Nowadays, it’s all about twerking.’
To grind also means ‘to work your a*s off’ in order to complete a task.
Girl, you haven’t even you started studying to your English exam. It’s on Monday! You’ve got to grind, hun!
Be careful about using grind in the UK as we use it to describe a s***l intercourse.
Sorry I could not write down all the letters as I got info the content is inappropriate 😅