This adjective describes events that occur suddenly and unexpectedly, without advance notice. In Luke 21:34, Jesus warns that the day of judgment will come αἰφνίδιος upon the unprepared, like a trap springing shut. Paul uses it similarly in 1 Thessalonians 5:3 to describe sudden destruction coming upon those who say "peace and safety." The word carries the force of something striking without warning, emphasizing the need for constant readiness.