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1.
The mental-emotional state when heavily attracted to or sprung on a girl; usually in regards to specific attributes, characteristics, or traits. May be synonymous/ interchangeable with "crushing" or "smitten."

Connotation usually suggests defeat, captivity, and submission.
Damn, you see that ass on Renee? Between that and those mean collarbones, I automatically got "the weakness."

or

- Hey bruv, how come you ain't make it to the Lucky Baldwin's last night?
- Date night with the lady...I think I have "the weakness."
by Matik Jan February 17, 2011