To please and affect someone by exhibiting a particular skill or manner. A noun or pronoun can be used between "impress" and "by." I'm very impressed by your ability to stay calm under pressure, which is certainly what we need in a receptionist. You really impressed the committee by your bold thinking. A: "Which of the interns should get the year-round position?" B: "I pick James—I was really impressed with his work ethic this summer."

to make someone notice one's good qualities. You impress me by your willingness to serve. We were all impressed by your candor.