The ounce abbreviation ‘Oz’ is not a valid Scrabble word. It is also not a legitimate word in SOWPODS and Words with Friends.
Ozone is the shortest word beginning with “oz” with only five letters.
However, a number of two-letter words beginning with “O” or “Z” are playable Scrabble terms. In fact, reversing the letters “O” and “Z” to form “Zo” would be acceptable. This word refers to a Tibetan yak and can alternatively be written as “Dzo,” “Zho,” “Dzho,” and “Dso.”
Knowing such two-letter words in Scrabble can make scoring high scores with few letters relatively simple.