third-person singular present zweifelt, past tense zweifelte, past participle <span class="searchmatch">gezweifelt</span>, auxiliary haben) to doubt, to be doubtful [with an ‘of’] 1931, Arthur...
krank ― seriously ill Selbstverständlich hat niemand ernsthaft daran <span class="searchmatch">gezweifelt</span>. ― Of course, nobody seriously doubted it. ernst Ernst ernstig ernstlich...