A fan that swings around and around is an example of a fan that oscillates.
When you go from delighted about an idea to angry about the idea and back again, this is an example of a time when you oscillate.
Origin of oscillate
- Latin ōscillāre ōscillāt- from ōscillum something that swings back and forth, swing probably from ōscillum small mask of Bacchus diminutive of ōs mouth ōs- in Indo-European roots
From American Heritage Dictionary of the English Language, 5th Edition