- Biology Having a hard shell or shell-like outer covering: testaceous echinoderms. (adjective)
- Biology Composed of a shell or shell-like material: a testaceous operculum. (adjective)
- Having the reddish-brown or brownish-yellow hue of bricks. (adjective)
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.