Walrus pups are able to swim at birth and weigh between 100 and 150 pounds. Most are only children (twin births are rare), and they stay with their mothers for two years. Eventually, their small young tusks will grow up to three feet long.
Definition of nuclear for Students. 1  1 : of, relating to, or being a nucleus (as of a cell) 2  2 : of or relating to the nucleus of the atom Fission is a nuclear reaction. 3  3 : produced by a nuclear reaction nuclear energy.  4 : of, relating to, or being a weapon whose destructive power comes from an uncontrolled nuclear reaction.
Definition of nucleus for English Language Learners. 1  biology : the central part of most cells that contains genetic material and is enclosed in a membrane. 2  physics : the central part of an atom that is made up of protons and neutrons. : 3  a central or most important part of something.