Indian, American- I'm willing to bet this entry no longer exists in any current encyclopedia.
Iron and Steel- I initially included this entry because I thought this big old gas guzzler would prove how far the car industry has come since the 70s. Then I did some research...
Iron Lung- Polio epidemics in the 40s and 50s paralyzed thousands, and the iron lung was the only means of breathing for many patients. Although positive pressure ventilators that allow patients to move about freely have been in use since the 1950s, there are still a few dozen iron lungs in use in the US today.
Isotope- "Isotopes are atoms of the same element that differ in atomic weight, or mass." I understand that because I majored in chemistry. But just because you understand the theory behind a concept doesn't mean you can apply the knowledge to everyday life. For instance, I have no clue what this illustration is showing:
The World Book Encyclopedia. Chicago: World Book-Childcraft International, 1979. Includes all photos and quotations.