Crack, as a secret message, is a term used to describe the process of decoding a coded message. It is usually done by using a cipher or code-breaking techniques. The term 'CRACK' is derived from the phrase 'cracking the code, ' which refers to the process of deciphering a coded message. Cracking a code can be done manually or with the help of computer programs. In the context of crossword solutions, the term 'CRACK' is used to refer to the process of decoding a secret message.