If I ain't strapped that means I took em off my Nike Airs

from Jay Z (Ft. Beanie Sigel, The LOX & Sauce Money) – Reservoir Dogs Lyrics on Rap Genius

Meaning

Strapped — Carrying some kind of firearm.
However in this line strapped carries a double meaning. Strapped meaning he carries a gun, and his straps on his trainers are done up. If he isnt strapped, that only means his trainers are a little loose. Don’t get confused with this if you piss this guy off. Consequences may be fatal.

He’s also referencing the fact that high top Air Forces have removable straps.

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