'Passer-by' definitions:

Definition of 'passer-by'

From: WordNet
noun
A person who passes by casually or by chance [syn: passerby, passer-by, passer]

Definition of 'Passer-by'

From: GCIDE
  • passerby \pas`ser*by"\, Passer-by \Pass`er-by"\, n. One who passes by, especially casually or by chance; one not directly involved in some action; a passer. [1913 Webster +PJC]