peek
(to look quickly and secretly)
- He peeked at her through a crack in the door.
- Close your eyes. No peeking! It’s a surprise.
peak
(the top of a mountain)
- Everest is the highest mountain peak in the world.
(the highest point or level)
- In the 1980s, he was at the peak of his popularity.
- Traffic is now at its peak.