What does “Last Sale” mean?

Last Sale is typically used to denote the most recent round or mixed lot trade transaction reported by a market center with eligible sale condition codes.

To facilitate a “Last Sale” calculation, NLS includes the sale condition modifier for both Nasdaq execution system and TRF transactions. The Sale Condition Modifier field consists of four levels. A trade should only be applied to the high, low, last sale, and volume calculations if all four sales condition modifiers so allow.