Oobleck
noun
Oo·bleck ˈü-ˌblek 
: a mixture of corn starch and water that behaves like a liquid when at rest and like a solid when pressure is applied
A quick tap on the surface of Oobleck will make it feel hard, because it forces the cornstarch particles together. But dip your hand slowly into the mix, and see what happens—your fingers slide in as easily as through water.
Katherine Harmon
Katherine Harmon
Word History
Etymology
after oobleck, a viscous green substance in the children's book Bartholomew and the Oobleck (1949) by Dr. Seuss (Theodor Seuss geisel)
First Known Use
1973, in the meaning defined above