Technical dictionary
UTXO (Unspent Transaction Output)
A discrete chunk of spendable Bitcoin controlled by a locking script/key condition—the unit of quantum exposure analysis for holders.
Definition
Bitcoin tracks value as unspent outputs. Each UTXO has a script that defines how it can be spent. Quantum risk is easiest to reason about per UTXO: has the public key been revealed? Was the address reused?
Portfolio risk is the aggregate of UTXO exposures plus custody operational design.