You can sell and rebuy, but it would be seen as a wash sale and they would likely disallow the loss offset if audited.
Wash sales are never clear cut. The price movement between sale and repurchase, the quantity of the repurchase versus the quantity of the sale and the time between sale and repurchase is never clear cut when it comes to treating something as a wash sale. If you can come up with a valid argument for doing the sale/repurchase, other than to reduce an existing gain, then you might get away with it if audited.
You could buy back a different stock and then it would be valid. This might work out for you if the stock you buy back is in a similar sector (sell BHP and buy RIO), even though they may exhibit similar relative price movements.
I can't remember the exact wording of what is a wash sale, but it essentially is related to selling and buying back to create a tax advantage, while having little or no change to your market exposure after the sell and rebuy. if audited.
