1. the state or fact of being impossible; something that cannot happen or be done
2. something that is impossible to do or achieve

Examples

• The impossibility of time travel has been debated by scientists for decades.
• She realized the impossibility of finishing the project in one day.
• Flying without wings is a physical impossibility for humans.
• The coach explained the impossibility of winning without teamwork.
• Many considered space travel an impossibility before the 20th century.
• The impossibility of the task became clear after several failed attempts.