Not typical, usual, or regular; not normal; deviant.
[Alteration (influenced by AB-1) of obsolete anormal, from Medieval Latin anormālis, blend of Late Latin abnormis (Latin ab-, away from; see AB-1 + Latin norma, rule; see gnō- in the Appendix of Indo-European roots) and anōmalus; see ANOMALOUS.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.