Similar meaning, but more formal:
* Enthusiasm: This is a common synonym, especially when talking about passion or excitement.
* Vigor: This emphasizes energy and strength in pursuing something.
* Zeal: This suggests intense fervor and dedication.
Similar meaning, but more informal:
* Relish: This emphasizes enjoyment and pleasure.
* Passion: This is a strong emotion, often associated with love or dedication.
* Fire: This implies intensity and excitement.
More specific meaning:
* Aplomb: If you want to emphasize confidence and self-assurance.
* Verve: If you want to emphasize energy and liveliness.
* Spirit: If you want to emphasize enthusiasm and a positive attitude.
Ultimately, the best replacement for "gusto" depends on the specific context and the meaning you want to convey.