What it means
一度に means doing or handling something all at once, in one batch, or during a single occasion. It commonly appears before a verb and often describes an action involving several items or a large amount. The phrase emphasizes that the action is not divided into multiple rounds.
Usage note
一度に describes how many things are handled in one action; it does not usually mean simply “once.” For the meaning “only once,” use 一度だけ, and for the meaning “never even once,” use 一度も with a negative expression.
How to use it
一度にVerb (ます-stem)ます
彼は一度に三枚の皿を運びます。
He carries three plates at once.
一度にVerb (dictionary form)
彼は一度に三枚の皿を運ぶ。
He carries three plates at once.