Occasional; infrequent—used to indicate something that happens once in a while (often in phrases like 'たまの〜' or 'たまに').
たまの休みだから、ゆっくり休んでいいよ。
Since it's a rare day off, you should relax properly.
たまの贅沢に美味しい料理を食べに行った。
For an occasional splurge, we went out to eat something delicious.
忙しい日々の中、たまに散歩するだけでも気分転換になる。
In busy days, even an occasional walk can be refreshing.