From Longman Dictionary of Contemporary EnglishRelated topics: Daily lifepasserbypass‧er‧by /ˌpɑːsəˈbaɪ $ ˌpæsər-/ noun (plural passersby) [countable]TTRDsomeone who is walking past a place by chanceThey sell drinks to passersby.Examples from the Corpuspasserby• The youngest died in the arms of a passerby, Boyle said.• A passerby said the noise was from a weddingcelebration.• But outside the batteredcongress building few passersby look twice at yet another standoff between demonstrators and riot police.• The robbery was witnessed by several passersby.• The catjumped to the floor, darted through the legs of several passersby, and disappeared into the bar.• The attackers were apprehended by an unknownpasserby, who chased the three youths and recovered the stolenbicycle.