harden; make hard
[구치다]
1. harden; make hard
To make a soft thing hard or stiff.
2. stiffen
To make one's facial expression, attitude, etc., gloomy or stiff.
3. strengthen; solidify
To make one's will, intention, resolution, etc., so strong that they do not change or shake.
4. solidify; strengthen
To not lose a good position or maintain advantageous circumstances.