うなる
うなる · unaru · JLPT N3 · verb-godan
to groan
unaru sounds like ooh, nah, ruh: the groan of someone who won't get up
Written 唸る. It covers any low drawn-out sound from the throat or a machine: a person groaning in pain, a dog growling, an engine humming. It is also the impressed hmm when something is really good, as in 唸るほどうまい, so good it makes you groan.