研磨, 磨碎
reduce (something) to small particles or powder by crushing it
摩擦, 磨擦
rub (something) together or against something else with a harsh, grating sound
苦干, 刻苦学习
perform a repetitive or tedious task
苦差事, 磨砺
a repetitive or tedious task or period of work
研磨声, 摩擦声
the action or sound of grinding