Turbo420answered grow question 3 years ago A node is defined as a point in which pathways intersect. In the case of growing; nodes are where new leaves intersect.
Further example:
as my plants grow I like to start of stress training at the 5th node.
This means that I will let the plant grow until looking up the plant I have 5 intersecting points of growth (nodes).
I hope this has helped, happy growing!