A.k.a. - Loose ends, dangling strings - are sources of stress.
An open loop is a situation which isn’t tied neatly back on itself. These are sometimes called loose threads or dangling strings. They are indicators of work to be done and situations that cannot stand.
Open loops are sometimes Projects in flight, sometimes areas laying in languish, needing more work. Sometimes open loops are systems whose components are not tied into one-another.
Regardless, open loops are sources of stress. They can be overwhelming when they are not wrangled. Open Loop discovery is the point of a Mind Sweep.