at once英英释义
Adverb
without delay or hesitation; with no time intervening;

"he answered immediately"
"found an answer straightaway"
"an official accused of dishonesty should be suspended forthwith"
"Come here now!"

simultaneously;

"he took three cookies at a time"

at once近义词
directly
immediately
forthwith
now
down
then
right away
instantly
straightaway
at one time
straight off
at a time
like a shot
in real time
soon
presently
shortly