What is an out-of-phase wave?

An out-of-phase wave refers to waves that experience a phase difference, meaning they do not align in time or position as they oscillate. When two waves are out of phase, their peaks and troughs do not occur at the same time. Specifically, this situation arises when one wave's peak occurs while the other wave's trough is present, leading to points of constructive interference at certain locations and destructive interference at others.

The option stating that waves occur at different times aligns with this concept of phase difference. In an out-of-phase scenario, while the waves may have the same frequency, they are misaligned, which is a critical characteristic of such waves.