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

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ad. Extremely, greatly: to an enormous degree.

ad. Shockingly.

ad. In an enormous degree.

In or to an enormous degree; extremely; vastly; beyond measure.

ad. extremely

"At the same time, he concedes he's not satisfied with Iraqi efforts to deal with the relentless violence, which he calls enormously challenging."

immensely    vastly    highly    very    greatly