to fall / (computing) to go down (as when a computer or application becomes unresponsive) / (electrical engineering, of a circuit breaker) to trip / (informal) to fail an examination

the sky

something empty / ineffectual / false

by heart, from memory, by rote

empty; vain; sky

a stone / (slang, electronics) a transistor

for grains of rice; one koku is equal to approximately 180 litres / (by extension, historical) for land of famous daimyo or samurai; one koku is also approximately 180 litres

counter for gemstones used as bearings in watches and other devices / (slang, electronics) counter for transistors, especially discrete ones

stone / needle made of stone / go stone / something solid but worthless / Short for 石見国 (Iwami-no-kuni): Iwami Province

stone; rock