A four-year period, a quadrennium.

a screw or worm gear having four equal threads and thus capable of being started in four places

A slotted plate for carrying the gears of a lathe. / A Petri dish, divided into four, and containing agar and other materials, used in the identification of bacteria.

paper marked out with squares

(of a sound system) Employing four independent channels or speakers.

(mathematics) A type of average, calculated as the square root of the mean of the squares, ie. Q=√x_1²+x_2²+...+x_n²/n.

(mathematics) a polynomial equation of the second degree.

A dance originating in the mid-1700s with four couples forming a square, rather much like the modern square dance. / The music for this dance.

(intransitive) To dance the quadrille.

Quadrille ruled graph paper, quad paper.