A split transaction in GnuCash is a transaction that posts to more than two accounts. All GnuCash transactions are internally represented as splits — even a simple two-account transaction has two splits. But the term “split transaction” typically refers to cases where a single transaction distributes its amount across multiple accounts.
For example, a paycheck deposit might split into gross pay (income), tax withholding (liability), retirement contribution (asset), and net deposit (asset). The total of all splits must balance to zero, enforcing double-entry bookkeeping.