any substance, organism, or process that causes malformations in a fetus. Teratogens include certain drugs (such as thalidomide), infections (such as German measles), and ionizing radiation
WordReference Random House Unabridged Dictionary of American English © 2026
te•rat•o•gen
(tə rat′ə jən, -jen′, ter′ə tə-),USA pronunciation n. [Biol.]
te•rat′o•gen′ic, adj.
- Drugs, Developmental Biologya drug or other substance capable of interfering with the development of a fetus, causing birth defects.
- terato- + -gen 1900–05
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