Here are some vocabulary words for preschool along with their definitions:

Ubiquitous: Present, appearing, or found everywhere.

Ephemeral: Lasting for a very short time.

Serendipity: The occurrence and development of events by chance in a happy or beneficial way.

Sycophant: A person who acts obsequiously towards someone important in order to gain advantage.

Pernicious: Having a harmful effect, especially in a gradual or subtle way.

Quixotic: Extremely idealistic; unrealistic and impractical.

Ephemeral: Lasting for a very short time.

Mellifluous: (of a voice or words) Sweet or musical; pleasant to hear.

Paragon: A person or thing regarded as a perfect example of a particular quality.

Voracious: Wanting or devouring great quantities of food; having a very eager approach to a particular activity.

Feel free to let me know if you'd like more words or if you have a specific theme in mind!