1º_ It is said of what has no flavor. From the Latin in- ( "denial, deprivation") shapur , oris ( "taste, good taste") . 2º_ By the above meaning, it is said of the work that it lacks grace, of spirit.
It means it lacks flavor. You don't detect any flavor. It can mean no salt, low salt or low sugar, no sugar. Unbrided, pitiful, unexpressed, cold.