We present a search for anomalous components of the quartic gauge boson coupling WWγγ in events with an electron, a positron and missing transverse energy. The analyzed data correspond to 9.7 fb-1 of integrated luminosity collected by the D0 detector in pp̅ collisions at √s=1.96 TeV. The presence of anomalous quartic gauge couplings would manifest itself as an excess of boosted WW events. No such excess is found in the data, and we set the most stringent limits to date on the anomalous coupling parameters a0W and aCW. When a form factor with Λcutoff=0.5 TeV is used, the observed upper limits at 95% C.L. are |a0W/Λ2|<0.0025 GeV-2 and |aCW/Λ2|<0.0092 GeV-2.