Evidence for rapid ordering in a supercooled Cu${}_{46}$Zr${}_{54}$ liquid, obtained from high-energy x-ray diffraction in a containerless processing environment, is presented. Relatively sudden changes were observed in the topological and chemical short-range order near 850 \ifmmode^\circ\else\textdegree\fi{}C, a temperature that is 75 \ifmmode^\circ\else\textdegree\fi{}C below the liquidus temperature and 465 \ifmmode^\circ\else\textdegree\fi{}C above the glass transition temperature. A peak in the specific heat was observed with supercooling, with an onset near 850 \ifmmode^\circ\else\textdegree\fi{}C (the same temperature as the onset of ordering) and a maximum near 700 \ifmmode^\circ\else\textdegree\fi{}C, consistent with the prediction of a molecular-dynamics calculation using embedded atom potentials. The chemical and topological ordering measured here are in agreement with predictions of a rapid development of chemically ordered icosahedral clusters in the supercooled liquid.