1 a: the white of an egg
b: egg albumin 2
2 archaic: endosperm
SENTENCE: It appears that the word albumen has a lot of different definitions, including the white of an egg, the albumin of eggs, a nutritive tissue in seed plants, and any of a large class of simple proteins.
NOTE: This word was the winning word of the fourth National Spelling Bee, which was won by Betty Robinson.