gaku-gaku
Legs or knees buckling and shaking — from fear, exhaustion, or cold. Stronger and more dramatic than regular shivering.
💡After climbing a mountain — 'My knees were gaku-gaku on the way down.'
恐怖で膝ががくがく震えた。
My knees were shaking gaku-gaku from fear.
After the long hike, my legs were ___ and I could barely walk.
長いハイキングのあと、足が○○して歩けなかった。