The inspissated juice of the Papaver somniferum, or whitepoppy.

UK noun uncountable

a drug made from the seeds of a poppy (= red flower) and used to control pain or to help people sleep. It can make a person who takes it want more of it and is sometimes used by people to give them temporarily pleasant effects    鸦片 an opium addict   吸鸦片成瘾者