Single malt whisky was a type of whisky made in a single distillery completely from malted barley.
Gabriel Lorca and Katrina Cornwell once shared a bottle of single malt while watching the Perseids meteor shower. Many years later in 2256, they shared another bottle over a friendly conversation aboard the USS Discovery. (DIS: "Lethe")
Single malt whisky was a favorite of Chief Miles O'Brien. Single malt Irish whiskey was served at O'Brien's birthday party in 2373, and in 2374, O'Brien and Worf wagered a bottle of bloodwine against a bottle of Scotch whiskey if Jadzia Dax beat Quark in a game of tongo. Quark was triumphant and O'Brien told Worf that he would like "Single malt. Preferably something from the Highlands". (DS9: "Change of Heart", "The Assignment")
The Species 8472 individual impersonating Boothby enjoyed single malt. When Commander Chakotay was captured on board Terrasphere 8, the replicant celebrated by toasting Earth with a single malt from 2175. (VOY: "In the Flesh")