Happening or done at exactly the same time as something else.
“The two membership discounts cannot be used simultaneously.”
“Both forms must be submitted simultaneously to be processed.”
Diagrams describing rules or processes sometimes note that two conditions or events occur simultaneously (e.g., two discounts cannot be applied simultaneously). Watch for this word when a question asks whether two benefits or actions can happen together, since it often signals a restriction rather than a combination that is allowed. Read the surrounding sentence carefully to see if simultaneity is permitted or forbidden.
Synonyms: at the same time, concurrently, together