(originally US, idiomatic) A big job; a difficult challenge.

(Britain) An official order forbidding press or broadcast discussion of a specified subject; a public interest immunity certificate.

(set theory) An object containing exactly two elements in a fixed order, so that, when the elements are different, exchanging them gives a different object. Notation: (a, b) or ⟨a,b⟩.

(cricket) the batsmen who bat in positions 5 to 7; often the poorer batsmen, the wicket-keeper and the bowlers who can bat best

(law) a court order entered at the beginning of a lawsuit to preserve a semblance of organisational order or to maintain the status quo pending the final disposition of the case

A ranking of items by a chosen attribute, especially a sequential hierarchy of nominal importance of people in royal courts and in governments.

The sequence of a collection of items (such as words in a dictionary) arranged in order by position in the alphabet.

(zoology) The natural hierarchy of social status and dominance occurring in a group of birds.

(cricket) the batsmen who bat in the first few positions

(Ireland, colloquial) The Restrictive Practices (Groceries) Order 1987, a law that (until revoked in 2006) prohibited below-cost selling.