Dictionary.net

Commerce, accounts. One in which a merchant or trader enters an account of all the money, or paper moneys he receives or pays. An entry of the same thing ought to be made under the proper dates, in the journal. The object of the cash-book is to afford a constant facility to ascertain the true state of a man's cash. Pard. n. 87.

n. A book in which is kept a register or account of money transactions.