BT Šab 15b(1) :אתו אינהו גזור על גושא לשרוף ואאוירא ולא כלום‏ : they came and decreed with regard to (terumah touching unclean) ground that he should burn (it); with regard to the air – nothing
See the entire entry for gūš, gūšā n.m. clod (of earth)