Wiktionary
n. 1 (context euphemistic English) A Martian. 2 (context humorous English) One of the supposed extraterrestrial occupants of UFOs.
Usage examples of "little green man".
I was already imagining Chesty Puller standing right there where that little green man was.
I had visions of a little green man with wings flourishing a night stick, arresting me for burglary.
A little green man put a slice and three anti-gravity disks on the counter.
The little green man flickered into life and we went across and opened the Lancia and got in and took Section 84 out of the glove compartment.
Many times she had sensed other bicycle riders' perplexity as she stopped at the lights and waited while they bumped up onto the pavement or raced through the traffic lights even though the little green man was showing, scattering pedestrians left and right.