a question about listening section

I see following statement in conversation 5, what does it mean?
“but it sure knocks the wind out of you”
Thank in advance

TOEFL listening lectures: A lecture from a life sciences class

it takes your breath away; it leaves you feeling weak; it surprises you.
(I don’t know what conversation you are talking about, so I can’t tell you which context is required here.)

Thank you for your help. See this URL please.“A conversation between two students in their dormitory during registration week | TOEFL Conversations | english.best

It doesn’t hurt, but it takes your breath away and leaves you feeling temporarily weak (when you fall out of the top bunk).

thank you very much, Beeesneees, and could you please tell me what is the meaning of “I’m just an aggie”

To be honest, I didn’t have a clue, however Wikipedia provides this explanation:
Aggie may be a diminutive form of Agricultural, which forms part of the name or historical name of many schools, particularly in the United States.

It seems that the student who says this is majoring in agriculture.