ithir, f. (gs. ithreach, pl. ithreacha). 1. Soil, earth; arable land, cornland. Tá an baile ar barr ithreach acu, they have stirred up the whole townland. 2. Land on which root crops have been grown in previous season. 3. (gs. as a.) Edaphic. S.a. cruimh 1.