(mathematics) The sequence in which the various operations in a mathematical expression are to be evaluated.

(Britain, Australia) a can opener.

A device used to open tin cans, usually by slicing the lid off. / (roller derby) A shoulder hit to the chest, usually accomplished while moving from a crouched to a standing position.

(mathematics) A half space that does not include the plane that bounds it

(idiomatic) To begin firing (weapons) at something or someone.

An uncovered fire.

plural of operating system

(uncountable) The state or quality of being opaque, not allowing light to pass through / (uncountable) The state or quality of being inaccessible to understanding.

(literally) Something that causes the eyes to open, or that opens the eyes. / (informal) Something that provides a sudden insight, or makes something clear that was previously mysterious.

Any simple step in a multi-step chemical engineering process; examples include distillation, evaporation, mixing, filtration, crystallization etc.