Definition of 堅い
- (adj-i) hard; solid; tough
- stiff; tight; wooden; unpolished (e.g. writing)
このふたは固くて取れない。
This lid is too tight for me to open. - strong; firm (not viscous or easily moved)
- safe; steady; honest; steadfast
- obstinate; stubborn
- bookish; formal; stuffy
固いこと言うなよ。
You don't have to be so formal.