at someone's command

at someone's disposal to use or instruct

由某人支配；聽從某人的指示

I shall defend myself with all the eloquence at my command.

我將用我所有的口才來為自己辯護(hù)。

by someone's command

in accordance with someone's orders

奉某人之命

word of command

(Military)an order for a movement in a drill

(軍)（軍事訓(xùn)練中的）口令，號(hào)令