1. Having no fixed or regular course; wandering: the erratic flight of a moth.
2. Lacking consistency, regularity, or uniformity: an erratic heartbeat.
3. Deviating from the customary course in conduct or opinion; eccentric: erratic behavior.
A rock fragment that has been transported by ice to a location other than its place of origin and that may range in size from a pebble to a large boulder.
[Middle English erratik, from Old French erratique, from Latin errāticus, from errāre, to wander; see ers- in the Appendix of Indo-European roots.]
er·rati·cism (-ĭ-sĭz′əm) n.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 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.