NP | ZK translation: body crabbed tight

[Mike Jing]

P197.15-23   I touched the screen for the receipt and then for account
activity and account summary and I wrapped the bills inside the flimsy
slips of toxic paper and left the booth, the stall, receipts and money
clutched in my hand. I didn’t look at the people in line. No one ever looks
at anyone in the ATM area. And I tried not to think about the security
cameras but here I was in my mind’s self-surveillance device, body crabbed
tight as I removed the money from the slot, counted it, organized it and
then recounted it.

What does "crabbed tight" mean here?
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