The Collaborative International Dictionary
Thummim
Thummim \Thum"mim\, n. pl. [Heb., pl. of th[=o]m perfection.] A mysterious part or decoration of the breastplate of the Jewish high priest. See the note under Urim.
Wikipedia
Usage examples of "thummim".
Urim and Thummim were given to Joseph Smith to help him decipher the hieratic writing, one assumes these magical jewels might have been supposed to aid something like clear vision and increased understanding.
He knelt down to find Urim and Thummim and put them back in the pouch.
And Nehemiah and Attharias told them not to share in the holy things until a high priest should appear wearing Urim and Thummim.