Having four sides.

The sound made by a duck.

To make a noise like a duck. / (intransitive) Of a queen bee: to make a high-pitched sound during certain stages of development.

(derogatory) A fraudulent healer, especially a bombastic peddler in worthless treatments, a doctor who makes false diagnoses for monetary benefit, or an untrained or poorly trained doctor who uses fraudulent credentials to attract patients

To practice or commit quackery (fraudulent medicine). / (obsolete) To make vain and loud pretensions.

Falsely presented as having medicinal powers.

(marketing, retail, logistics, manufacturing) Initialism of quick response. / Ellipsis of QR code. / (medicine) Initialism of quiet room. / (pressure cooking): Initialism of Quick Release.

(US, modern British and Australian, short scale) A thousand trillion (logic: 1,000 × 1,000^4): 1 followed by fifteen zeros, 10¹⁵.

(figuratively, slang, hyperbolic) Any very large number, exceeding normal description.

square-shaped / (mathematics) of a polynomial, involving the second power (square) of a variable but no higher powers, as ax²+bx+c. / (mathematics) of an equation, of the form ax²+bx+c=0.