means the characteristic vocal sound a cat makes, or an imitation of it.

from An imitative word — what linguists call onomatopoeia — formed to echo the sound itself, like 'moo' or 'baa.' English earlier had 'mew' (recorded since at least the 16th century), with 'meow' a later variant; nearly every language reaches for a similar shape, from French 'miaou' to Japanese 'nyaa,' each ear hearing the same small noise slightly differently.