A hobby in which you watch people with your phone, mainly for online dating website when you swipe and watch people’s profile /pictures just for fun, not really into actual conversations or engaging.
People watching is when u go around and watch people that u've never met before and, based on their actions, movements, and gestures, guess what kind of people they are and what they do.
Let's go to Whole Foods - I'm in the mood for some beautiful-people-watching.
H: Ooh, look at that dude pick out his protein-rich drinks. I bet his name is Nate and he's going kayaking after this.
Z: Hmm, do you think that girl with the shiny hair is his girlfriend or his sister?
H: I'm gonna say that's his mom. She has very nice skin for her age, though.