κάθισμα · kathisma — LSJ
part on which one sits: in pl., buttocks, Sch. Aeschin. 1.126.
seat, Simp. in Ph. 347.9, Pall. in Hp.Fract. 12.278C.
base of a still, Zos.Alch. p.224B.
sinking, settling down, of a wall, Apollod. Poliorc. 150.1.
sediment, Sch. Nic. Al. 95.