A thin and usually jagged space opened in a previously solid material. / A narrow opening. / A sharply humorous comment; a wisecrack.

Highly trained and competent. / Excellent, first-rate, superior, top-notch.

(obsolete) One who excels; the best.

(intransitive) To form cracks. / (intransitive) To break apart under force, stress, or pressure. / (intransitive) To become debilitated by psychological pressure.

(intransitive, idiomatic, often with 'with') To continue at a task briskly or promptly. / To continue apace. / (transitive, dated) To put on.

Obsolete form of crack.

(chemistry) The thermal decomposition of a substance, especially that of crude petroleum in order to produce petrol / gasoline. / The formation of cracks on a surface. / The production of a crack sound.

That cracks; that produces a sharp sound as of something splitting or breaking. / (colloquial) Great. / (colloquial) Enjoyable.

(Britain) Very, usually associated with praise.

present participle of crack