The term used when one would like to announce to those around them that they are leaving to smoke a joint, particularly when in the presence of authority figures.
(In front of the proctor) Hey guys, anyone up for a nature walk?
When a couple slips away from a party/gathering to do a variety of sexual acts
Person 1: Where'd Ethan and Emma go?
Person 2: On a nature walk
Person 1: Again?
when you and some friends step out of a party or a resteraunt to go smoke pot.
Guy1 - where's Brian?
Guy2 - he went on a nature walk with Frank.
A session (not necessarily a walk) throughout time and space that weed always plays a large part in.
At boyscout camp nature walks were an hourly occurrence.
A walk into the woods to urinate or poop
"Tourist: Are there any restrooms at this rest area?"
"My wife: No, there's only a nature walk."