of the highest/first order

of the first order

Of the greatest importance, significance, or magnitude. You have to study Shakespeare because he is a poet of the first order. We need to close the highway immediately—this is an emergency of the first order.

of the highest order

Of the greatest importance, significance, or magnitude. You have to study Shakespeare because he is a poet of the highest order. We need to close the highway immediately—this is an emergency of the highest order.

of the first order (or magnitude)

used to denote something that is excellent or considerable of its kind.

In astronomy, magnitude is a measure of the degree of brightness of a star. Stars of the first magnitude are the most brilliant.

of the highest/first ˈorder

of a high ˈorder

of the best, worst, most extreme, etc. type: It was a scandal of the first order.