Waterfall projects can have all of the important attributes of agile: collaboration with customers, feedback and refinement, intermediate deliverables, etc. They don’t always work that way, but neither does agile. The main difference is the amount of analysis and design done in advance of writing code, and the relative emphasis placed on formalities and artifacts.

In practice agile, especially variations of Scrum, have grown to include rituals (stand-ups, sprint planning) and artifacts, which can turn those projects into coding with no guardrails or clear destination.