LSJ
ατος, τό, embankment, dyke enclosing an area, PPetr. 3 p. 339 (iii BC), Ostr. Bodl. i 245 (iii BC), PTeb. 61 (b).167 (ii BC).
area enclosed by dykes, PCair. Zen. 182.7, 362.24 (iii BC), PTeb. 13.12, 84.3 (ii BC).
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)