A slasher is a basketball player (typically a guard, but also possibly a forward) who primarily drives (slashes) to the basket when on offense. A slasher is a fast and athletic player, who is looking to get close to the basket for a layup, a dunk or to drop in a teardrop shot for a high-percentage two-point play (this style of play is commonly referred to as slashing).
Slashers usually take more free-throw shots than other players due to the increased amount of contact made on them as they constantly and aggressively run towards the basket (many gain extra free-throws by "drawing fouls", which is deliberately causing contact with a defending player), and they may spend many hours working on increasing their free-throw percentage.
Many players who begin as slashers typically develop their game (especially their jump shot), as age and injuries occur, which may prevent them from being as effective as a slasher (for example; Michael Jordan and Kobe Bryant both developed a fadeaway jump shot as they got older).