to remonstrate; to admonish (someone) for; to advise (someone) not to; to warn against
忠臣は主君を諫めた。
The loyal retainer admonished his lord.
友を諫めて、過ちを正させた。
He admonished his friend, making him correct his mistake.
彼は若き音楽家が信念を曲げないよう諫める。
He advises the young musician not to compromise his beliefs.