Having a thick, heavy, or hardened shell.(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.
Use "hard-shell" in a sentence
"Sis Belle was what was called a hard-shell Baptist, loyal to the death and disdainful of rivals."
"Many of the people who are in the forefront of the effort to promote marriage equality are members of the clergy in a lot of religious denominations ranging from mainstream Protestant to hard-shell Roman Catholic."
"We talk about Tex-Mex food but the more I think about it, it is actually Cal-Mex cuisine, from crumbly hard-shell tacos to velvety-rich guacamole to the eye-opening margarita, that has shaped our preferences for south-of-the-border fare."