plural of operating room

plural of opinion poll

(education) Referring to exams in which external resources such as textbooks, glossaries, study notes, calculators, etc. may be used.

(idiomatic) Something of which salient aspects are obvious or easily interpreted.

plural of open cluster

plural of open book

plural of open book decomposition

(mathematics, topology) A decomposition of a 3-manifold into a link and a fibration over the circle by surfaces bounded by that link.

plural of open compound

(uncountable) A chess opening characterized by the moves 1.e4 e5, in which both White and Black move their king's pawn to the fourth rank with their first move.