under [phrasal verb] [I] [informal] - to accept someone's power over you; allow yourself to be beatenThe boys were encouraged to knuckle under and get trained as chippies, mechanics or electricians.The government, he declared, would never again knuckle under to the demands of trade unions.
KNUCKLE
Meaning of KNUCKLE in English
Cambridge English vocab. Кембриджский английский словарь. 2012