- Resistant to pressure; not readily penetrated. (adjective)
- Physically toughened; rugged. (adjective)
- Mentally toughened; strong-minded. (adjective)
- Requiring great effort or endurance: a hard assignment. (adjective)
- Performed with or marked by great diligence or energy: a project that required years of hard work. (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.