Definition
Bitcoin is a cryptoasset and peer-to-peer payment system whose public blockchain records transfers of the native unit, bitcoin, without a central ledger operator.
In market context
Bitcoin uses proof of work and a distributed network of nodes to validate blocks under shared protocol rules. Control of a bitcoin address depends on private keys, while transaction finality is assessed through accumulating network confirmations rather than reversal by a central administrator. Its market price can be highly volatile, and ownership introduces custody, transaction-fee, network, fraud, and regulatory risks.
Risk context
Bitcoin transfers are generally irreversible, and loss or disclosure of the controlling private key can result in permanent loss of access.
Source
Use the primary source for fuller regulatory or market context.