资料来源 : Webster's Revised Unabridged Dictionary (1913)

Passenger \Pas"sen*ger\, n. [OE. & F. passager. See {Passage},
   and cf. {Messenger}.]
   1. A passer or passer-by; a wayfarer. --Shak.

   2. A traveler by some established conveyance, as a coach,
      steamboat, railroad train, etc.

   {Passenger falcon} (Zo["o]l.), a migratory hawk. --Ainsworth.

   {Passenger pigeon} (Zo["o]l.), the common wild pigeon of
      North America ({Ectopistes migratorius}), so called on
      account of its extensive migrations.

资料来源 : WordNet®

Ectopistes migratorius
     n : gregarious North American migratory pigeon now extinct [syn:
          {passenger pigeon}]