‖n. [ L., let it be printed. ] 1. (Law) A license to print or publish a book, paper, etc.; also, in countries subjected to the censorship of the press, approval of that which is published. [ 1913 Webster ]
2. (R. C. Ch.) Permission granted from a designated eccliastical authority to publish a book or other document; -- required by church law for Catholics, especially ecclesiastics, who wish to publish. [ PJC ]
3.Hence: Official approval for some proposed activity; as, a contract this large needs the imprimatur of the legal department. [ PJC ]