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Webster 1913 Edition

Noun.

[NL., fr. Gr. [GREEK], [GREEK], monster +

-oma

(Med.)

A tumor, sometimes found in newborn children, which is made up of a heterigenous mixture of tissues, as of bone, cartilage and muscle.

teratoma ‎(plural teratomas or teratomata)

(pathology) A benign or malignant tumour, especially of the gonads, that arises from germ cells and consists of different types of tissue such as skin, hair, or muscle.
- 1972, Patrick O'Brian, Post Captain:
  ‘What is a teratoma?’ asked Jack, holding the object in his hand. ‘A kind of grenado?’ ‘It is an inward wen, a tumour: we find them, occasionally, in the abdominal cavity. Sometimes they contain long black hair, sometimes a set of teeth: this has both hair and teeth.’

type of tumour

teratoma f ‎(plural teratome)