Lewis & Short

Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.

autŏmătus, um (os, on), adj., = αὐτόματος, self-moving, voluntary, spontaneous: plausus, Petr. 50, 1.
Hence, subst.: autŏmătŏn or -um, n, a self-moving machine, an automaton, Vitr. 9, 9; Petr. 54, 4; 140, 10; * Suet. Claud. 34 fin.