A clear boundary or limit that won't be crossed
This is my line in the sand. I won't compromise on it.
interrupt
He cut in while I was speaking.
damage that happens naturally over time through regular use
The marks on the floor are just wear and tear from years of foot traffic.
It's slightly code; a mild, informal way to say it's chilly.
It's a bit nippy out there. You might want a jacket.
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To start showing symptoms of an illness
I think I am coming down with a cold; I've been sneezing all day.
Credit https://www.facebook.com/photo?fbid=857700760522617&set=a.354219590870739