Cask Strenght means high alcohol. Whisky is typically diluted with water to about 40% ABV. However, cask strength stuff isn't messed with, so it can remain anywhere between 50-75% ABV. As a rule of thumb, expect a cask strength dram to be around 60-65% ABV.

What is considered cask strength?

Cask-strength whiskey is bottled from the barrel, completely unadulterated (meaning it hasn't been diluted with water) and is generally between 60 to 65 percent ABV.

What is another term for cask strength?

Cask strength (also known as barrel proof/barrel strength) is a term used by whiskey (often spelled "whisky" outside of Ireland and the United States) producers to describe a whiskey that has not been substantially diluted after its storage in a cask for maturation.