This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

ad. Without any delay; in an instantaneous manner.

In an instant; in a moment; in an indivisible point of duration.

ad. without any delay

"Even if they don't take you seriously at first, the fact that they don't brush you off instantaneously is important."

instantly    in a flash    outright    right now    immediately