When you are awestruck, the weight of someone or something lands on you so hard that you almost stop. It is the feeling that this person, this place, this task is more important, more difficult, or more serious than you were ready for. You may go quiet. You may just look. There is respect in it, and often a little fear — not horror, but the sense that you should not treat this lightly. You can be awestruck by a person (a surgeon at work, a teacher who has spent a life on one hard subject) or by a thing (an old temple, a mountain, a problem that turns out much bigger than it first looked). Though actually everyday speech now stretches it toward wonder too: people say they were awestruck by a view even when they are not afraid, only stunned. The tidy core is still the heavy one — respect for size and seriousness. It is a strong word. Save it for moments that knock the air out of you, not for a sandwich you liked. Younger speakers sometimes use it as a louder “wow”; careful writing keeps the respect-and-weight meaning.