A colloquial concessive particle meaning 'even if' or 'even though', roughly equivalent to 〜ても or だって in casual speech.
雨が降ったって、試合は中止にならないよ。
Even if it rains, the game won't be canceled.
彼は忙しいたって、手伝ってくれるだろう。
Even if he's busy, he'll probably help.
高くたって、この靴はすごく丈夫だ。
Even if it's expensive, these shoes are very durable.
An emphatic colloquial form meaning 'no matter how' or 'however much', stressing that the result remains unchanged; also seen as 〜ったって.
どんなに謝ったって、彼の気持ちは簡単に戻らないだろう。
No matter how much you apologize, his feelings probably won't easily return.
金を積んだって、そんなことは許されない。
Even if you put up money, such a thing won't be allowed.
いくら練習したって、才能が必要な場合もある。
However much you practice, there are times when talent is necessary.