The absorption of electromagnetic radiation of a specific frequency by an atomic nucleus that is placed in a strong magnetic field, used especially in spectroscopic studies of molecular structure and in medicine to measure rates of metabolism.
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.