A stream that has no permanent tributaries.

(colloquial, dated) A neat and tidy arrangement or organization; a perfect order.

(law) A court order allowing a plaintiff to go to someone's premises and seize documents (entry must be with that person's permission, but if refused would be a contempt of court). Used in extreme cases when a prospective defendant might destroy documents, especially computer files, if they knew a court case was coming.

plural of first order stream

(stock market) A conditional order placed with a stockbroker (or similar) to close one's position if the market drops (or rises in some cases) to a specified price level.

(Britain, informal) A court order forbidding publication of any information that could identify a child involved in legal proceedings.

(idiomatic) Exactly what is necessary or useful in a given situation; something very beneficial or desirable.

(surveying) An optimal network design within a computer. It involves choosing an optimal reference system and revolving it around a certain real number.

(set theory, order theory, loosely) A set that has a given, elsewhere specified partial order. / (set theory, order theory, formally) The ordered pair comprising a set and its partial order.

(set theory) A partial order.