Give or take a few H's, N's, and G's; an onomatopoeia with multiple possible uses including:
1) The sound one makes when having a heart attack.
2) The sound one makes when straining -- for instance, when attempting to lift a heavy object, or when constipated.
3) The sound one makes when presented with something overpoweringly cute or moe
. The full extent of its meaning is open to a wide range of interpretation, ranging from the suppression of an innocent squeal of delight to the sound of an orgasm.
The sound of a whale trying to ride a bicycle.
"I say, old chap, is that a whale riding a bicycle?"
"Why, yes it is."
"What do you suppose that sound is it's making?"
"I believe it is HNNNNG."
An onomatopoeia describing an undesirable situation.
"So I was walking down the road with my girlfriend and I passed by my ex... Hnnnng!"