Creation of or increase in a short position in a given series of options.
A transaction in which the seller's intention is to create or increase a short position in a given series of options. 
Creation of or increase in a short position in a given series of options.
A transaction where the seller of an option becomes the... <a target=_blank href='http://www.finance-glossary.com/terms/opening-sale.htm?id=1058&ginPtrCode=00000&PopupMode=false' title='Read full definition of opening sale'>more</a>