However, you could use a few options depending on the context:
* "Siwt ffurfiol" - This translates to "formal suit" and is the most general equivalent.
* "Siwt briodas" - This means "wedding suit" if you're referring specifically to a tuxedo for a wedding.
* "Siwt gwasanaeth" - This means "service suit" and can be used if referring to a tuxedo worn for a specific service or event.
It's important to note that these options may not be as precise as "tuxedo" in English, as Welsh doesn't have a specific word for it. You may also need to clarify the specific context to ensure the best translation.