Late harvest wine
Also known as late picked, wine made from grapes that have been left on the vine longer than usual. Usually an indicator for a very sweet or dessert wine.

Lees
Wine sediment that occurs during and after fermentation, and consists of dead yeast, grape seeds, and other solids. Wine is separated from the lees by racking.

Legs
The tracks of liquid that cling to the sides of a glass after the contents have been swirled. Often said to be related to the alcohol or glycerol content of a wine. Also called tears.

Lightstruck
A tasting term for a wine that has had long exposure to Ultraviolet light causing "wet cardboard" type aroma and flavour.

Litre (US - Liter) 
A metric measure of volume equal to 33.8 ounces.

Look
A tasting term for the casual sensory evaluation of a wine.