From WordNet (r) 2.0 (August 2003) [wn]:
hobo
n : a disreputable vagrant; "a homeless tramp"; "he tried to
help the really down-and-out bums" [syn: tramp, bum]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Hobo \Ho"bo\, n.; pl. Hobos or Hoboes. [Of uncertain
origin.]
A professional tramp; one who spends his life traveling from
place to place, esp. by stealing rides on trains, and begging
for a living. [U. S.] -- Ho"bo*ism, n.
Syn: tramp; bum; vagrant; knight of the road.
[Webster 1913 Suppl.]