* Caomhnóir: This is a good general translation, encompassing the idea of a protector or keeper. It's probably the closest single word equivalent.
* Cosaintóir: This translates more literally to "protector" and might be suitable if the guardian's role is primarily defensive.
* Cúramóir: This means "carer" or "one who takes care of," and is appropriate if the guardian's role involves nurturing and looking after someone.
* Dhlíodóir (in a legal sense): If you're talking about a legal guardian, this word, meaning "lawyer" or "legal representative," might be more fitting.
To choose the best word, you need to consider the specific role of the guardian. For example, a guardian angel might be best described as a *caomhnóir*, while a legal guardian would be a *dlíodóir*.