Exhibiting a milky iridescence like that of an opal.

(informal) To speak about things rashly or foolishly, when it would be better to stay silent.

(ophthalmology) An instrument for examining the interior of the eye (that is, for ophthalmoscopy).

A company that sells package holidays.

(finance) Negative operating income.

In operation; that operates. / Involved in an operation.

present participle and gerund of operate

The opinion of the public, the popular view.

Effectual or important. / Functional, in working order. / Having the power of acting; hence, exerting force, physical or moral; active in the production of effects.

An employee or other worker with some particular function or skill. / A spy, secret agent, or detective. / A participant in an operation.