A member of the ginger family with a very tough but elusively scented rhizome which must be peeled before use.
The best substitute is water-packed slices of galangal sold in jars, generally exported from Thailand. Otherwise, use slices of dried laos (soaked in boiling water for 30 minutes) or as last resort, powdered laos (1 teaspoon = 2 ½ cm - 1 in)