What's the closest word Classical Latin (Greek?) would have used for mobile machines, even if they don't have a human shape?
(NB: this answer is adapted slightly from another answer I gave here)
I think perhaps automaton or automatum.
I’m not aware of any Roman writings on robots as such, whereas the Greeks wrote surprisingly frequently about robot-like beings.
Thus, we have automatos / αυτοματος (sg), automata / αυτοματα (pl) attested in ancient Greek literature as referring to self-acting, autonomous, mechanical beings. Some examples include:
- The self-opening gates of Olympus (αυτομαται πυλαι) in Homer, Iliad, 5.749
- The self-moving tripods Hephaestus made, referred to as οι αυτοματοι
/ the autonomous ones, in Homer, Iliad, 18.376
- A reference to “miraculous automatic puppets” (τα αυτοματα των
θαυματων) in Aristotle, Generation of Animals, 734b11
An example of its use in a compound form is αὐτοματοποιητικά / automatopoietika - the title of a section of Philo of Byzantium's (also known as Philo Mechanicus, fl. ca. 250 BC) engineering manual, dealing with the construction of mechanical toys and diversions.
Therefore, I think the nominalised Greek adjective automata is broad enough to encompass a variety of mechanical "mobile machines", human-shaped or not.
Clearly adopted from Greek, automatum does actually appear in Latin works, although very rarely. In Petronius, it does seem to refer to an automaton or at least a clockwork toy of some sort:
ne per parietem automatum aliquod exiret / lest some automaton leap
out of the wall (Satyricon, 54)
In Suetonius, however, it seems to be more of an ordinary mechanical device, not intended to look or act like a human but nevertheless to work under its own power:
si automatum ... parum cessisset / if a device ... had worked
insufficiently (Lives of the Caesars: Claudius, 5.34)