What is as much spirituous liquor as is usually drunk at once; as, a dram of brandy; hence, a potation or potion; as, a dram of poison. Shak called?

dram — As much spirituous liquor as is usually drunk at once; as, a dram of brandy; hence, a potation or potion; as, a dram of poison. Shak. (Webster's 1913.)