Te Aka Māori-English, English-Māori Dictionary and Index is a brilliant resource, even if you’re just an amateur Te Reo Māori enthusiast like me.
You can search in Māori or English.
A bonus are the rather wonderful examples of the word in context:
hei aha [tāu]!
I don’t care what you say! – used to emphasise that the speaker will take no notice of a suggestion because it has no value.
Kāore au e pai ki a Timi, he pākira rawa nō tōna rae. Hei aha tāu, he tangata hūmārie ia. / I don’t like Tim. He’s too bald. I don’t care, he’s a handsome man.
Aurelia’s recently used the phrase “Tau kē nei” – this is so cool, this is so neat. A great term to use when you’ve discovered something you think is worth sharing. And Te Aka deserves it big time!