What does maith is leath an mean in English?

"Maith is leath an" is not a complete phrase in Irish. It's missing the second part of the proverb.

The full proverb is:

"Maith is leath an chéad"

This translates to:

"Good is half the battle"

It's a proverb that emphasizes the importance of a positive attitude and good intentions in achieving success.