1. hard; solid; tough
esp. 固い and 堅い for wood, 硬い for metal and stone
2. stiff; tight; wooden; unpolished (e.g. writing)
3. strong; firm (not viscous or easily moved)
4. safe; steady; honest; steadfast
5. certain; assured; highly likely
of a predicted outcome
6. obstinate; stubborn
7. bookish; formal; stuffy
8. solid (shape or stones)