n. pl. pla·teaus or pla·teaux (-tōz)
1. An elevated, comparatively level expanse of land; a tableland.
2. A relatively stable level, period, or state: Mortgage rates declined, then reached a plateau.
intr.v. pla·teaued, pla·teau·ing, pla·teaus
To reach a stable level; level off: "The tension seemed to grow by degrees, then it plateaued" (Tom Clancy).
[French, from Old French platel, platter, from plat, flat; see PLATE.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.