Douglas Harper's Etymology Dictionary
Wiktionary
vb. (context intransitive idiomatic slang English) To spend time doing nothing in particular.
WordNet
v. spend time in a certain location or with certain people; "She hangs out at the corner cafe"
Usage examples of "hang out".
Avoid narrow paths commonly travelled by animals - that is where ticks hang out.
They sat there facing me and they let their tongues hang out the sides of their mouths as they panted more demurely.
Those who hang out in my SFFnet newsgroup and provide facts, ideas, and general support (in this case, a double dose of thanks to Cecil, Howard, Julia, Rachel, Tom, and Susan.
But one that suspected, that contempt of life in them, might proceed from some Passion of the mind, and supposing they did not contemne also their honour, gave counsell to the Magistrates, to strip such as so hang'd themselves, and let them hang out naked.
I have never seen the inside of the building at Microsoft where the top executives hang out, but I have this fantasy that in the hallways, at regular intervals, big red alarm boxes are bolted to the wall.
Expensive toys gave her a pretext to hang out at swanky craft fairs and be admired, and meet such as Simon and Jim.