From Longman Dictionary of Contemporary Englishdoorknobdoor‧knob /ˈdɔːnɒb $ ˈdɔːrnɑːb/ noun [countable] 
DHHa round handle that you turn to open a door
DHHa round handle that you turn to open a doorExamples from the Corpus
doorknob• Thus resolved, Theodora focused her flashlight on the brass doorknob on the panelled door.• Thick and wavy-grained like smoke, but thicker, like water, and a glass doorknob.• A second slab of beef has crawled out of bed and found his doorknob.• Then one day I came upstairs and caught her with her hand on my doorknob.• Everything was designed, including wastepaper baskets and the doorknobs.• With the bolt drawn and one hand on the doorknob, I paused to note the time.• Wasn't there a dark smear on the doorknob of the long room? 