If you are impetuous, you do things very quickly, before you have really thought. You say yes, you buy the ticket, you send the message — and only afterwards do you sit down and ask, “Wait — was that wise?” The word can describe a person, and it can describe what the person does: an impetuous choice, an impetuous remark, an impetuous rush of feeling. The heart of it is not simply speed. Plenty of quick people are careful; an impetuous person is quick because a feeling is shoving them. Though actually, it is not always a scolding word. Writers still use it for young love, sudden bravery, a leap that later looks lucky. In everyday talk, many people reach for impulsive instead; impetuous sounds a little more like a book, and a little stronger, as if the rush has force in it. It is not the same as impatient (that is about waiting badly), and not the same as rude.