A lookback option that comes with a time window (e.g., 1- 3 months), known as the partial lookback period, allowing the holder to set or reset the strike price at the best level attainable during the partial lookback period. Thereafter, the option turns into a standard American-style option (American option). The strike price can be reset on a specific evaluation date if the option is, or becomes, out-of-the-money. Because the lookback period doesn’t span the entire life of the option, the partial lookback option usually sells for a price higher than that of a standard option and lower than that of an ordinary lookback option.

Broadly, partial lookback options are also referred to as reset options.