It can also be used to mean "fair" or "just" in some contexts.
Here are some examples:
* "Mae'r tywydd yn gweddol dda heddiw." (The weather is fairly good today.)
* "Mae'r fwyd yn gweddol dda." (The food is suitable/appropriate.)
* "Mae'n bwysig bod y penderfyniad yn gweddol." (It is important that the decision is fair/just.)