If you embark on an activity that people haven’t experienced before, you’re entering uncharted waters or uncharted territory.
Have you combed your teeth today?
“I’ll just have a slither.”
When you limit or control something you can be said to rein it in. Take care with the spelling. Sometimes people write “reign in” but that’s nonsense.
It’s quite difficult to come up with a complete A-to-Z series of posts because not quite all the letters of the alphabet offer suitable material.
In UK English we use the word quite as an adverb to mean “completely” and we also use it to mean “to a certain extent”.