A2giving a lot of attention to what you are doing so that you do not have an accident, make a mistake, or damage something: Be careful with the glasses.Be careful where you put that hot pan.Be careful to look both ways when you cross the road.Michael is a very careful worker.After careful consideration of your proposal, I regret to say that we are unable to accept it.He's in a really foul temper so be careful (about/of) what you say to him.Cautious and vigilantPaying attention and being careful