Untempered
Wilson's Dictionary of Bible Types [1]
Ezekiel 13:10 (b) The term is taken from building materials to describe careless methods or wrong teachings in building GOD's people as a nation. Faulty building materials will not stand the test of the storms of years. They will crumble under pressure. So, the nation of Israel, and also the church, must be built according to GOD's provisions and His divine will. (See also Ezekiel 22:28).
King James Dictionary [2]
UNTEM'PERED, a. Not tempered not duly mixed for use not durable or strong.
International Standard Bible Encyclopedia [3]
un - tem´pẽrd ( תּפל , tāphēl ): Used of mortar in Ezekiel 13:10-15; Ezekiel 22:28 . Ṭāphēl probably refers to mortar made with clay instead of slaked lime. In the interior of Palestine and Syria walls are still commonly built of small stones or mud bricks, and then smeared over with clay mortar. The surface is rubbed smooth and is attractive in appearance. This coating prolongs the life of the wall but requires yearly attention if the wall is to stand.
Ezekiel uses the practice to typify the work of false prophets. They build up stories and make them plausible by an outward semblance to truth, while, in fact, they are flimsy, unreliable prophecies, resembling the walls described above, which can be broken down by a push or a heavy rain storm.