Definition
To spend considerable time and effort fruitlessly in a hopeless endeavor.
Origins
After the stereotypical behaviour of wolves howling at the moon in folklore.
How People Actually Use It
The combination of farting and screaming after performing the Fukushima Release Valve. When the gas passes out of the man and into the woman's nose, she immediately starts trying to buck him off her head leaning back and screaming. The sound produced is that of a wolf howling in agony.
"That was the loudest Howl at the Moon I have ever heard! She must really be pissed!"
Source: Urban Dictionary