Endorsement in blank refers to a signature on a financial instrument, such as a cheque, without any restriction or direction as to whom the instrument is payable. This type of endorsement is often used when the payee is unknown or when the instrument is being transferred to a third party. There are several synonyms for endorsement in blank, including blank endorsement, general endorsement, open endorsement, and unrestricted endorsement. These terms all refer to the same type of endorsement and are interchangeable in most contexts. It is important to note that endorsing a financial instrument in blank can be risky, as it essentially allows whoever holds the instrument to cash it.