metric ounce

noun3

1. •
   A metric approximation of the ounce.
2. •
   25 grams.

   • It would probably be convenient also to retain the ounce, the metric ounce being defined as equal to 25 grams, or one-twentieth of the metric pound. — 1901
3. •
   30 grams.

   • Thirty grams or a metric ounce (the American ounce is 28 grams) — 1882